Added a millisecond countdown inside of the clkinit.

Updating the countdown in clkhandler. I started initial value as 10ms.
Stub out areas for different scheduling algorithms to run
Added FCFS scheduler and changed insertion into ready queue to take algorithm into account.

Also cleaned up implementation of multiple schedulers.  Scheduling definitions moved to scheduler.h
Scheduler constant added to conf.h file.
Refactored RR Quantum
Merge branch 'master' of https://github.com/benNThompson/xinu-arm

Conflicts:
	system/resched.c
added SCHUDULER constant to compile with various schedulers.
Fixed issue where round robin was not restoring the inturrupt mask and exiting if time quanta had not passed.

- Also added a return so rr will not context switch in the above case.
Added new shell command
Fixed typo
Added measuresched as shell command
Fixed things
Fixed another silly mistake
Merge pull request #9 from benNThompson/master

Schedulers merge