More cleanups and style fixes
Add a note about a gotcha
Stick log message in return data
Allow passing path of local file as log message arg.
General smell removal
Fix some deprecation warnings in tests
Various fixes for subtle bugs in virtual unit management.

 - adding included units didn't bumb child count correctly
 - the way moving worked broke due to attempting to iterate a
   lazy single-use iterable twice
 - added more tests
Merge branch 'master' of https://github.com/EHRI/ehri-rest
Merge pull request #51 from mikesname/master

Various cleanups