Reorganisation

[piakushin]

Changing bob project structure:

• crate bob
  • bob
  • bob-common
  • bob-backend
  • bob-grpc
  • bob-tools

[piakushin]

Compilation time comparison, 8 cores 4.6GHz:

test/branch	current	master
cargo build	1m 31s	1m 39s
cargo build --release	2m 18s	2m 23s
cargo check (full)	1m 03s	1m 02s
cargo check(1 change in grinder.rs)	1.39s	2.66s

Cargo check completes faster on workspace because it doesn't recompile all mods, only subcrate with changes.