copy over code from maurits branch on plone.app.collection for topic migration and make it work in here
ops pdb. also sorted imports
No longer need to checkout p.a.querystring for this branch.
minor pep8 in topic migration
fix topic logger name
Add Topic upgrade notes
Support migrating non-recursive path queries.
Support migrating multiple path queries.
Removed unneeded commented out line.
Forgot to remove warning about multiple paths.
Make slightly less complex, trying to please flake8.
Migrate to Dexterity-Collections (not Archetypes-Collections from plone.app.collection)
enable migration to DX-Collections in the form and fix tests to use dx-collections
use folderish migrator if collections are folderish
revert accidental change to folderish collections
allow migration even if old FTI is missing
Check for subtopics and folderish Collections before migration.
fix test and add more info on subtopic-migration
Merge pull request #198 from plone/migrate-topics-to-dx

Migrate topics to collections