[Scenario] Use capability for Save All support

Changes to platform in support of
nasa/MCT-Plugins#72 move methods
which support Save All to a capability.
Changes here reflect this, and use
explicit object management in preparation
for explicit notification from view
about which components have changed.

This should allow components to indicate
that changed activities found in
collections should be included in Save All
actions (their omission is the root cause
of nasa/MCT-Plugins#72) without requiring
a potentially deep search of descendants'
dirty flags.
[Scenario] Remove unused field, imports
[Scenario] Merge in latest from master
[Scenario] Update ObjectManager during merge
[Scenario] Fix Save All in Scenario

Ensure Save All works as intended in
Scenario View by using an appropriate
ObjectManager type.

Note that Save All in a scenario still
fails after a refresh due to timeline
staleness.
[Scenario] Resolve scenario Save All issues

Use Scenario as the object manager for
embedded timeline views. This ensures
that updates made to components in the
timeline view by way of staleness
updates are reflected in the invocation
of a Scenario-level Save All.
[Scenario] Move stale listener to superclass

Move the stale listener used to refresh
Timeline views with incoming changes up
to the superclass shared with Scenario
view, such that both Scenario and
Timeline update with the same strategy.
This allows, for instance, the cost
graph shown in the scenario view to
stay up-to-date with changes to
individual timelines.

This supports resolution of remaining
instances of nasa/MCT-Plugins#56
Merge pull request #86 from VWoeltjen/mctPlugins72

[Scenario] Resolve Save All/Refresh issue