Merge: introduce nit_env.sh to setup the shell environement

The script `nit_env.sh` tries to auto-magically configure PATH, MANPATH and bash completion for users. The point is to be as portable and simple a possible for the final used has he just has to write

~~~
$ source misc/nit_env.sh
~~~

and get a working setup.

Moreover, if `install` in given as argument, then the script register itself to the user `$HOME/.profile`.

~~~
$ source misc/nit_env.sh install
~~~

One advantage is that the script invocation is registered in `.profile`, thus future evolutions of the script will be automatically used in future sessions of the users.

Pull-Request: #1784
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --combined README.md
index fb0e27c,5b35eea..0df1fcc
--- 1/README.md
--- 2/README.md
+++ b/README.md
@@@ -1,4 -1,5 +1,4 @@@
 -Nit is a statically typed object-oriented programming language.
 -The goal of Nit is to propose a statically typed programming language where structure is not a pain.
 +Nit is an expressive language with a script-like syntax, a friendly type-system and aims at elegance, simplicity and intuitiveness.
  
  Nit has a simple straightforward style and can usually be picked up quickly, particularly by anyone who has programmed before.
  While object-oriented, it allows procedural styles.
@@@ -13,37 -14,40 +13,37 @@@ Some Nit features
   * Light and clear syntax.
  
  
 -Requirement:
 +Requirements:
  
 -      * gcc           http://gcc.gnu.org/
 -      * pkg-config    http://www.freedesktop.org/wiki/Software/pkg-config/
 -      * ccache        http://ccache.samba.org/        to improve recompilation
 -      * libgc-dev     http://www.hpl.hp.com/personal/Hans_Boehm/gc/
 -      * graphviz      http://www.graphviz.org/        to enable graphes with the nitdoc tool
 -      * libunwind     http://nongnu.org/libunwind
 + * gcc                http://gcc.gnu.org/ (or a compatible C compiler)
 + * pkg-config http://www.freedesktop.org/wiki/Software/pkg-config/
 + * ccache     http://ccache.samba.org/        to improve recompilation
 + * libgc-dev  http://www.hpl.hp.com/personal/Hans_Boehm/gc/
 + * graphviz   http://www.graphviz.org/        to enable graphs with the nitdoc tool
 + * libunwind  http://nongnu.org/libunwind
  
 -Those are available in most linux distributions
 +Those are available in most Linux distributions
  
 -    # sudo apt-get install build-essential ccache libgc-dev graphviz libunwind pkg-config
 +    $ sudo apt-get install build-essential ccache libgc-dev graphviz libunwind-dev pkg-config
  
 -Important files and directory:
 +Important files and directories:
  
 -      benchmarks/     Script to bench the compilers
 -      bin/            The Nit tools
 -      bin/nitc        The Nit compiler
 -      bin/nit         The Nit interpreter
 -      bin/nitdoc      The Nit autodoc
 -      c_src/          C code of nitc (needed to bootstrap)
 -      clib/           C code needed by nitc to compile programs
 -      Changelog       List of change between versions
 -      contrib/        Various Nit programs (may or may not be useful)
 -      doc/            Documentation
 -      examples/       Program examples written in Nit
 -      LICENCE         License of the software
 -      misc/           Some additional file for commons text editors and tools
 -      tests/          Non-regression test-suite
 -      lib/            Nit standard library
 -      Makefile        Bootstrap the Nit tools
 -      NOTICE          List of the authors
 -      README          This file
 -      src/            The Nit tool sources (written in Nit)
 + * benchmarks/        Script to bench the compilers
 + * bin/               The Nit tools
 + * c_src/     C code of nitc (needed to bootstrap)
 + * clib/      C code needed by nitc to compile programs
 + * contrib/   Various Nit programs (may or may not be useful)
 + * doc/               Documentation
 + * examples/  Program examples written in Nit
 + * lib/               Nit standard library
 + * LICENCE    License of the software
 + * Makefile   Bootstrap the Nit tools
 + * misc/      Some additional files for commons text editors and tools
 + * NOTICE.md  List of the authors
 + * README     This file
 + * share/     Common resources used by tools
 + * src/               The Nit tool sources (written in Nit)
 + * tests/     Non-regression test-suite
  
  
  How to start:
@@@ -52,11 -56,11 +52,9 @@@
      $ bin/nitc examples/hello_world.nit
      $ ./hello_world
  
- You can put the `bin/` directory in your PATH
+ You can source `misc/nit_env.sh` to setup your environment like PATH, MANPATH and bash completion.
+ To have your environment automatically configured at login, just source it with `install` as argument.
  
- Using bash completion with Nit tools:
- 
-     $ echo source /absolute/path/to/misc/bash_completion/nit >> ~/.bash_completion
-     $ source ~/.bash_completion
+     $ . misc/nit_env.sh install
  
 -More information:
 -
 -      http://www.nitlanguage.org
 +More information: <http://www.nitlanguage.org>