Remove unused classes, traits
first pass on #70 - somewhat painful converting AppDescription to something JSON friendly.
For wordcount a REST query of /appmaster/0?detail=true results in a JSON structure of {"appId":0,"appDescription":{"name":"wordCount","conf":[],"dag":{"vertex":["Split","Sum"],"edge":[["Split","HashPartitioner","Sum"]]}}}
use map's returned collection and convert to list
Getting a better idea of how the serialization/deserialization of types should work assuming we can automate. ActorRef's deserialization should really be path -> ActorSelection -> ActorRef
Another pass on AppDescription JSON conversion
Use class canonical names
Merge remote-tracking branch 'upstream/master'

Conflicts:
	core/src/main/scala/org/apache/gearpump/cluster/ClusterMessage.scala
	project/Build.scala
Merge pull request #71 from kkasravi/master

REST API to retrieve a given AppMasters DAG