Add ClockAlarm and MicroAlarm and Alarm

[tyler-gilbert]

ClockAlarm will be based on a countdown as will MicroAlarm. Alarm will be based on Time (date and time).

[tyler-gilbert]

Just add MicroAlarm and Alarm.

MicroAlarm is based on MicroTime. Alarm is based on Time.

[tyler-gilbert]

These will go in chrono namespace.