GrampsLocale: Use module-specific logger for grampslocale.py

Fixes double-logging problem reported by Tim Lyons.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@21235 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
GrampsLocale: Replace use of get_language_string with GrampsLocale.get_language_dict

Permits sorting by localized language name.
Also hides the language code, which the user doesn't really care about.
Removes get_language_string from libtranslate.py, no longer needed.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@21236 4ae1f11a-8b86-4847-b8af-ab372f36d1fd