Refactored alarm_alert.xml and DigitalClock.java

DigitalClock is now linear layout with
gravity center_horizontal
padding top
padding bottom

ampm field visibility in case it is not used is GONE instead of INVISIBLE

this closes #72

this also fixes the issue introduced by restyling when digital clock was
on 2 lines.

bumped version 2.0.9

	modified:   AndroidManifest.xml
	modified:   res/layout/alarm_alert.xml
	modified:   src/com/better/alarm/view/DigitalClock.java