A unit of work is a simple storage with write lock/unlock.
The manager/package now share a unit of work instance.
The unit of work is used to prevent shared dependencies from being cloned/copied "at the same time" fixing issue #81.
The prune and version resolving algorithm was also not correct. It now resolves versions correctly, fixing issue #57.
- Fix I/O errors caused by copying/clone repos simultaneously to the same dest.
- Optimize the clone/copy step by avoiding it if the last resolved resource is the same.
- Fix failing test (at least on my windows machine)
- Add some more tests
- Fix CS.
