add feature ContractCalls callgraph

[tintinweb]

this is basically a variant of surya graph that is useful for large codebases. It only shows contract-to-contract call to allow someone to quickly understand how the contracts are interacting together. edge color and weight denote how many calls there are from one to the other component (and therefore how tightly coupled they are).

this is a super hacky copy of surya graph and we might want to refactor this at some point. :)

legend (there's a dark and a bright theme):

• normal node = contract
• shape: box3d = library
• shape: arrow = interface (didn't know what to use there. maybe better to use diff. colors?)
• shape: rounded, dashed = "undefined" contracts (or external stuff)

[tintinweb]

we could also think about hiding calls to undefined contracts (often class attribs or because of safemath etc.) the remove some clutter

[maurelian]

It feels a bit immature, but maybe that's OK to move into develop. Here's my comments from using it on github.com/consensys/erc1400 (graph output below):

• The legend should be updated.
• The two colored arrows are confusing. Does it just change color when there's more calls?
• Are these only external calls, or are some internal calls included?
• Yeah, I think a color would be better than a shape for an

Also, I think the command list is getting too long and confusing. I think we should consider consolidating all the commands that output graphviz markup into graph, and adding an arg to specify which type of graph.

[GNSPS]

We should probably close this, right @tintinweb ?

[tintinweb]

oh yeah :)