Fixes initial migrations of entries, crm, and contracts

Put crm models in entries migration so circular dependencies won't take
several migrations to fix up. Used a depends_on clause in contracts so
that it will run after the entries migration. Had to add a second
entries migration for entrygroup to tie contracts and entries together
Merge branch 'develop' of github.com:caktus/django-timepiece into feature/786-initial-migrations
Document changes in migrations
Merge pull request #787 from caktus/feature/786-initial-migrations

Fixes initial migrations of entries, crm, and contracts