Allow ms value for AlarmClock()

this commit allows AlarmClock() to take values in milliseconds.
can be useful for skinners (see http://forum.xbmc.org/showthread.php?tid=156191&pid=1337513#pid1337513 )
needs a ms suffix for time parameter (for example, "300ms"), the original behaviour isn´t changed. (still uses minutes when time parameter is an integer)
other way would be to move that to TimeStringToSeconds()