Add QTLua as an option for a script component

[Ryan Swart]

http://www.nongnu.org/libqtlua/ is an alternative to the QTScript
module. Personally, I prefer game scripting in Lua to Javascript (er,
QTScript :P), and having an option of scripting languages can only
help attract people to developing with Gluon.

A short chat in IRC raised concerns of the fact that this requires a
lua interpreter to run, but as I see it lua is small and simple, and
there aren't really different implementations across platforms, so it
shouldn't be a major issue.

Anyhow, hope it makes for interesting discussion!