CMFM: User-defined date/time format

Allow the user to select the date/time format to use.
JIRA: CYAN-863
Issue: https://jira.cyanogenmod.org/browse/CYAN-863



Change-Id: I13730e8c82e5de96645c9c70f244535eb449e261
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>