Introduced Vertex and VertexHandler classes

Signed-off-by: Frank Mayer <frank@frankmayer.net>
1) Use Vertex class instead of Document class
2) reflect name-change deleteGraph() -> dropGraph()

Signed-off-by: Frank Mayer <frank@frankmayer.net>
make some functions protected

Signed-off-by: Frank Mayer <frank@frankmayer.net>
Cleanup of class and added stub methods for those that are not supported in GraphHandler, but inherited from DocumentHandler
Added phpdoc class version info (@since)
Signed-off-by: Frank Mayer <frank@frankmayer.net>
Added phpdoc class version info (@since)

Signed-off-by: Frank Mayer <frank@frankmayer.net>
Added graph-api example

Signed-off-by: Frank Mayer <frank@frankmayer.net>
Generated Docs

Signed-off-by: Frank Mayer <frank@frankmayer.net>