Support for godepgraph

[dlsniper]

As an extension of #969, it would be interesting if the plugin would support godepgraph to be generated for arbitrary files in the project (just like Java has right click -> Diagrams -> Show Diagrams

[dlsniper]

If there's any open-source sample that uses the implementation in IDEA to generate this in another language plugin, can it be linked here for reference? Thank you :)

[zolotov]

@dlsniper I don't know any