cgame: fixed cg_drawTimeSeconds and added leading zero, refs #283

cg_drawTimeSeconds 1 displays seconds, 0 is disabled. Also use ':' instead
of '.' for second delimiter, and always use double digit for sec, min. Use
double digit for hours unless the 12 hours format is selected.
Merge pull request #50 from Spyhawk/clock

cgame: fixed cg_drawTimeSeconds and added leading zero, refs #283