Fix various bugs and add "floating IP handler" to the OpenStack provider

This commit contains:

- Fixes of typos in docstrings and comments
- 7 various small bugfixes
- a small feature (add "floating IP handler" to the OpenStack provider)
- a small addition to the DUMMY provider

If I should break up this pull request into several pull requests and/or I should write Jira tickets, just let me know.