project workspace and linting using clippy

[debris]

This pr introduces following changes:

• all projects are now a part of the same workspace. Workspace documentation
• updated tools/draw_graph.sh script to work despite this bug:
  • cargo graph does not work with cargo workspaces kbknapp/cargo-graph#33
• created new tools/clippy.sh script which is running clippy linting without modyfing the codebase and despite the following bugs:
  • https://github.com/Manishearth/rust-clippy/issues/1326
  • https://github.com/Manishearth/rust-clippy/issues/1330
• fixed few clippy warnings, more to come in next prs

tested clippy version: 0.0.98, requires rust nightly