Generate the .pot file from the correct Glade files.

It was being generated from .glade files (just one, no longer used)
instead of the ones with .ui extension.
Remove unused Glade file.
Use locale module to get Glade file translated.

See:
https://docs.python.org/2/library/locale.html#access-to-message-catalogs
Update changelog.
Merge branch 'bugfix-lp1078306-i18n-issue' of https://github.com/rivaldi8/gtg

Fix #30, fix #31

Conflicts:
	CHANGELOG
	GTG/taskbrowser/gtd-gnome.glade