Improve test coverage of erroneous Booker/TermTime data cases

The code coverage results of !7 (merged) (which adds comparison operations for depts, sites, buildings, floors and rooms) show that many of the cases where Booker returns badly-formatted results are not covered by the tests. Although the hope is that Booker will never return such results in practice, we should test these scenarios to make sure the comparison operations handle such cases gracefully (in case they do ever occur).

Extended to include TermTime responses too

Looking at coverage, missing tests for:

• booker.py - auth() and couple of edge-cases
• comparison.py - invalid data being compared, use assertion func added by !18 (merged)
• termtime.py - already 100%
• state.py - loading configuration
• sync.py - main process handler - may be tricky
• core.py - minor func usage - add a couple of extra doctests
• __main__.py/__init__.py - probably ignore

Include test coverage of 409 booking conflicts.