Give more details about the AIM version

Every time the AIM is built, now a new `version.c` file will be dynamically generated, with the information of the environment where the AIM was built.

This will allow us to have a more precise control on the AIM versions that are deployed. Here is an example output:

    # ./aim -v
    AIM server version 1.6.1
      Git: defb12e6957fcc68632064696650a531a337a3bf
      Build: 2013-06-11 18:55
      Platform: Linux 2.6.32-358.6.2.el6.x86_64 x86_64

/cc @enricruiz @apuig @abelboldu