Move locale initialization into main.vala: Bug #731231

Need to move locale/gettext initialization into the very beginning of
main() in order to ensure it's respected throughout the run of the
application.
Localize Week view day header labels: Bug #731723

The ordering of the Week view day header labels needs to be available
for localization.

Because strftime() returns unsightly leading zeroes for some of the
new formats, a utility method to strip them (and some tests) are
included.