The old bash-based parsing code was way too complex. Replace it with Lua.

When two domains alias the same name (or one aliases another), display a
meaningful error message like:

    Failed to alias domain 'foo' as 'bar', name already taken by
    domain 'baz'.

Solves a recursive dependency problem.

While we're at it, also fix the description string.

Based-on-patch-by: lemoer <git@irrelefant.net>

The domain configs are not checked yet, and not used for anything.

Based-on-patch-by: lemoer <git@irrelefant.net>

This will allow us to use its content from other languages than Lua as
well.

PKG_FILE_DEPENDS caused the whole site repo to be hashed to determine if
gluon-site needed rebuilding. While this is normally no problem,
alternative build setups sometimes put the Gluon repo inside the site repo,
causing long build times and parallel build failures.

Having two POT files will only cause confusion.