Saving multiple licences implemented
Validating duplicates
Merge
Corrected errors
SN uniqueness check in bulk
Removed copypasted validators
After save redirect to licence list
Merge pull request #222 from zefciu/RBM-108

Implemented adding multiple licences
Unassign License actions in transition
Merge pull request #224 from quamilek/unassing-licence

Unassign License actions in transition
Fix flake8 errors.
Merge branch 'develop' of https://github.com/allegro/ralph_assets into invoice-licence

Conflicts:
	src/ralph_assets/urls.py
	src/ralph_assets/views.py
Fix Flake8 errors
Add missing user in asset save