lua-factory: don't iterate on lua env table

When calling a c function in lua, the top of the stack is the
environment table of lua, _G.

This patch fixes the case where GrlNetWc options was not passed
at grl.fetch and grl.unzip functions.

https://bugzilla.gnome.org/show_bug.cgi?id=733289
thetvdb: fetch show in cache with case insensitive

https://bugzilla.gnome.org/show_bug.cgi?id=733287
Updated Brazilian Portuguese translation