Fixed bug in settings.py
Make database paths configurable from settings.ini

This adds a new requirement: dj-database-url. Database URLs can be set
from either `settings.ini` or env variables.
Improved settings.ini documentation
Added row highlighting of selected session in inventory view
Added entity and entityrole model creation to import utility
Added Ajax paging to regid view
Replaced broken tags in db

- Replaced broken tags in db
- Added script to create some useful entries in db for testing purposes
Check for existing session in swid inventory view

Show an error message when viewing the inventory view for a device that
has no sessions.

Fixes tnc-ba/strongTNC#158.
Added missing load statement
Added swid measurement controller
Added software-id field to model and updated swidimport command
Improved bulk create for tags / files / sessions
Raise an exception on import if a tag has no tagcreator
Support for camelCase API fields
Use "uri" for URL_FIELD_NAME in API
Added nested entity roles to TagSerializer
Enabled filtering on TagSerializer
Implemented API endpoint for adding SWID tags
Improved validation in API endpoints
More & better tests for API endpoints