Continuing main_screen, fixed (?) wchar things

- Updated TODO. Leaks are apparently fixed.
- Better interface to add children to GUI base components.
- Fixed, fucked, refixed and fucked and fixed str to wstr. It works with
the following tradeoff: to wchar converted string is incorrectly
PRINTED, but it's correctly RASTERIZED.
- cstr_to_wstr helper now asks for a const std::string.
- GUI button asks for text const std::string.
- GUI label now asks for const std::string instead of const wchar_t*
(much more convenient).