Bind.parse() fails when access mode is specified

Due to an off-by-one error only input without given access mode (like `/host:/container`) could be parsed, see added test.
Also added support for read-only (`:ro`) specifications.

I would also like to change the thrown exception to `IllegalArgumentException` in `Bind.parse()` and `Volume.parse()`.
Is this OK, should I amend this PR with it?