Time sensor by Martin Aspeli <optilude@gmx.net>

This is a sensor based on the Clock and LTVUptime to support clock.display
from psi-small. It makes Clock a bit more flexible:

 - Adds "uptime" output
 - Adds "time" output (formatted time, like hh:mm[:ss])
 - Adds configuration parameter to show seconds on digital clock
 - Adds short and long date format
 - Exposes the show-date, show-uptime and show-seconds parameters as outputs
 - Fixes a bug whereby daytime would always show "pm" for 24 hour clock

Note:

 - i18n translations are incomplete! If you want to add a translation, please
    send it to me!
