[Scenario] Add Procedure URL to Activity model

Add a field to store a procedure's URL
to the model of Activity. This supports
nasa/MCT-Plugins#131
[Scenario] Add visual controls for Procedure link
[Scenario] Add padding around Activity links

Add a few pixels of padding around Activity
links shown in its Info View.
Merge pull request #148 from VWoeltjen/mctPlugins131

[Scenario] Add link to Procedure in Activity
[Scenario] Permit Move between repositories

Make an exception to the Remove Manifestation
policy for repository components in the
specific case where policy is being considered
as part of a drag-drop Move action.
[Scenario] Disallow Link between repositories

Disallow drag-drop linking between repositories.
[Scenario] Allow reordering within repositories

Permit the Link drag-drop action in a
repository in the special case where a
repository already contains these
components, to permit reordering.
[Scenario] Remove unneeded dialog

Remove unneeded dialog which appears when
moving between repositories; this is now
clarified by the Move option that appears
when dragging between repositories.
Merge pull request #149 from VWoeltjen/mct179

[Scenario] Update repository behavior to match move/copy/link