Make LR self contained

This PR is initially for discussion. 

It adds a Lua binary (5.2) to the `bin` directory, so LuaRocks runs completely independent of the Lua host installation, to reduce chances of interference. Basically the next step after moving the binaries out of the PATH (was also to reduce interference).

Not sure whether is worth the hassle. Just a possibility; maybe install Lua (5.1/5.2/Jit) itself as a rock as LR then no longer depends on Lua being present on the host.

please comment.