Adds comprehensive tests for:

1. `touch`
2. `remove_dir`
3. `remove_rec`
4. `move_file` and `move_rec`
5. `copy_file` and `copy_rec`
6. `check_empty_dir`
7. `makedirs_rec`

Discovered a corner-case bug in `touch` which renders it broken for existing
files and directories. So the corresponding tests are disabled and with TODO
markers to fix the bug and enable them.

Author: jonasbardino