Add Typesafe Config PolledConfigurationSource
Moved Typesafe source to module archaius-typesafe
Element expansion clobber check doesn't need to know number of elements, since the bracked-based indexing scheme would be an illegal key, anyhow.
Merge remote-tracking branch 'origin/master' into typesafe-config
Upgrade typesafe-config 1.2.0->1.2.1
Merge pull request #180 from mnadel/master

Add Typesafe Config PolledConfigurationSource.