Activity list, DateFormat, i18n improvements

ActvsListAdapter and BlockListAdapter now use localized strings to
display activity flags, as well as colors defined in colors.xml. Doesn't
look too shabby, in my opinion.

DateFormat stuff has been revamped; they're all in Utils now. There's
now FixedDateFormats in Utils, for parsing, and DateFormats for display,
which is an enum.

A few other things have been localized. Untranslatable strings have been
split off into donottranslate.xml for better readability.

And a random new click listener in ActvsListAdapter. I'm so sorry this
is all in one commit.