rhbz1174516 - enable more flexible file mappings rules in podir and gettext project

- when push, podir project will log warning on locales don't have any translation file but won't rely on directory convention
- when push, gettext project will log warning on po file missing locale but won't rely on file name convention
Optimization: strip untranslated entries if merge type is NOT import (i.e. auto)

- if after the stripping there is no entries left, we can skip the REST call for that translation file
Merge pull request #40 from zanata/rhbz1174516-podir-filemapping

rhbz1174516 - enable more flexible file mappings rules in podir project