Feed CMake constants to Focus

It uses config.h.cmake to fill a .h file with constants that
are inside the CMakeFiles.txt file. Then, that .h file is
provided to Focus by using a custom VAPI.
Change unsaved saves message

Wow. Much HTML. Such Elementary.
Add I18N template

Finally, an internationalization system has been added using
gettext. Each string on the code has been replaced with gettext
_("") function. A template has been generated using the command.
A translation to Spanish is also added.