Make commitlog backup to run in the background.  In snapshot restore, restore up to n commitlog files.
N is set in config file and defaulted to 10.
Merge remote-tracking branch 'upstream/1.2' into 1.2

Conflicts:
	priam/src/main/java/com/netflix/priam/defaultimpl/PriamConfiguration.java
	priam/src/test/java/com/netflix/priam/FakeConfiguration.java
Clean up some spaces and logging
Merge pull request #278 from timiblossom/1.2

1.2