Display units on root containers when they are added.
Added uncommitted relation icons
Test that units are displayed on root containers when they are added.

Fixed updating of containers that don't exist yet.
Select containers when units are placed on them.
Merge pull request #541 from huwshimi/display-root-container-units

Display root container units

Fixed bug #1367138 so that added units appear on root container tokens.
Merge pull request #543 from huwshimi/keep-containers-selected

Select containers when units are placed on them

Fixes bug #1367423 where container tokens were deselected when units were added to them.
Add onboarding message.
Show/hide onboarding appropriately.
Cleanup localStorage in testing.
Simplify localStorage flag.
Pull out diamond styling into mixin.
Test fix.
Merge pull request #545 from makyo/remove-relation

Added uncommitted relation icons

This includes some code reorganization to be more in line with D3 style and to make the relation rerendering easier to work with.
Merge pull request #546 from kadams54/commit-onboarding

Add onboarding message to call attention to commit button.
Add flag to enable containers on all providers.
Merge pull request #551 from frankban/containers-feature-flag

Add flag to enable containers on all providers.

Introduce the `containers` feature flag.