Lua modulefile support #573

Lua modulefile support has been asked at several occasions by the community (on the mailing-list or during conferences).

So it seems good for Modules to also support Lua modulefiles in addition to Tcl modulefiles.

Best way to achieve this is to ensure the maximum compatibility with Lmod: for users and sysadmins not to have to learn a specific Modules-Lua syntax.

So the Lua modulefile support should:

• all Lua Modulefile Functions defined by Lmod
• use same precedence mechanism than Lmod when facing Tcl and Lua modulefiles within modulepaths