GrampsLocale: Protect another setlocale instance
Determine Paths at Runtime

Uses GRAMPS_RESOURCES to override the root location of the Gramps data files (which would normally be $(prefix)/share).
In setup.py install, writes $(prefix)/share to gen/utils/resource-path, installs that file, then deletes it again from the source tree. The presence or absence determines whether Gramps is running from the source directory or from an installation.

Const.py is now a static file; const.py.in is no longer used. Note that because importing const into setup tried to initialize things that we don't want initialized, VERSION is removed, and imported from gramps.version -- a file which will be added in the next change. Consequently, this commit will not run.
Move VERSION, VERSION_TUPLE, major_version from const.py to version.py

As noted in the previous change, importing const into setup.py tried to initialize GrampsLocale and ResourcePath, which won't work. Since all we want is the VERSION string, move that to a new file, gramps/version.py
Install image files to $(prefix)/share/gramps/images

Instead of $(prefix)/share/gramps/icons/hicolor, which was an old (early Gtk2) theming requirement.