cLock: added option to highlight the upcoming calendar events

With this option, today's, and after 8pm also tomorrow's events can
be displayed bold and in different colors.

Patchset 1-7- Initial commits
Patchset 8  - Fix strings
            - Fix preference summaries for color preferences
            - Set feature defaults to off
Patchset 9  - Fix bold preference

Change-Id: I209442c0747ed5984f312c85c6744400a83b17fb