Complete support for Rust Cargo manifests

[pombredanne]

Description

@ritiek added a basic support for Rust Cargo files in #1426
This ticket is to complete the work and in particular add first licenses and dependencies then other fields then possibly support for lock files, etc...
See also #1424

[amaizyng]

I'm working on this as part of Code Day Labs with Mahin and Yasseen

[amaizyng]

Adding comment to help clarify the scope of this issue for future work.

Issues can be found in cargo.py (see #TODO comments).
A. Support glob patterns found in cargo workspaces*
B. Load (extracted license statement) as a notice_text
C. Add file refs: readme, include and exclude
D. Add extra package data found such as version control and commits (see details below that TODO)
E. Add missing “source” vs “dependencies” and checksum

*I am currently focused on supporting glob patterns found in cargo workspaces. Will be splitting into a sub-issue after I have a clearer solution.