Add maven goal for REST api documentation

Springdoclet builds REST api documentation with
'mvn javadoc:javadoc' command.  The command
'mvn site' builds the overall class documentation
to accompany the REST api endpoints.
Merge branch 'master' of https://github.com/Lab41/Dendrite
Fix graph import to close file InputStreams

Fixes "java.io.IOException: Too many open files"