more cleanup in all files

with this PR the cleanup of salad should be done. after this the PRs will be smaller and only add or correct functionalities.

again, this does
- general cleanup, pep8 cleanup, indentation fixes, numbering scenarios
- add $ at the end of regular expressions
- fixes for small bugs
- add missing tests for until now untested steps
- add support for "within X seconds" (+ tests)
- add support for "contains" to compare with partial text (+ tests)
- add some general util steps (general.py, browser.py)
Why not `datetime.now()`?