Add web front-end mockup

Add static file handler and framework for web front-end to gremlin-server.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	gremlin/gremlin-server/src/main/java/com/tinkerpop/gremlin/server/GremlinServerHandler.java
Refactor static file handler in separate class
Merge remote-tracking branch 'upstream/master'

Conflicts:
	gremlin/gremlin-server/src/main/java/com/tinkerpop/gremlin/server/IndexPage.java
Merge remote-tracking branch 'vsu/master'