Write an audit tool that uses Callgraph

[jubnzv]

We could use the Callgraph module implemented in #1144 to create a tool that helps auditing smart contracts.

Desired functionality:

• A CLI option to don't show pure functions call on the .dot dump. This is usable to reduce the noise when analyzing imperative code.
• Show changes in the imperative state of the contract for each procedure/transition. Read, write, and read-write (update) operations of fields should be shown differently.
• External calls, event, exceptions on the graph.
• Show clusters of procedures/transitions based on fields they access (if procedures commute, i.e. do not share common state, it should be clearly observable from the call graph).

[anton-trunov]

The more filtering options this contract map tool supports the better. Remote reads also should be marked explicitly.

[jjcnn]

Moving to v0.14 due to lack of time.