enable translation of the "Endnotes" section header-word for these reports

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@22171 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
Add translation to gen.merge.diff

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@22172 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
GrampsLocale: When checking translations check full locale first

So that e.g. en_GB will be preferred over en if en_GB is in fact the
desired translation.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@22173 4ae1f11a-8b86-4847-b8af-ab372f36d1fd