Chaned the namespace name from 'lua' to 'blua'.
'blua' stands for 'bla_lua' (which would be too long and tedious to type, and
'blua' is nice because it sounds and looks almost like 'blue' and is short enough).

Rationale:
While it works and is (somewhat) clear and to the point about what we are doing in
there, it's a bit too arrogant to use that name and it's possibly misleading the
user/reader to think we are somehow part of official lua code/lua c++ binding ect.