[Satellite] Latency when creating a large number of satellites

[VWoeltjen]

The create wizard for satellite objects makes it easy to create large groups of satellites all at once. The downside of this is that it all occurs on the UI thread, which may cause substantial latency if the user has selected a lot of satellites.

Two options come to mind to address this:

• Show a blocking progress dialog while creating satellites, allowing the user to cancel out
• Do the work on a background thread. The user will see their collection created with satellites appearing in it over time (probably several at a time)

The latter lets the user return to use of MCT more quickly, but may be confusing and may open the door to other unusual bugs (what happens if the user adds other things to the collection while satellites are still being created in it on a background thread?)

[VWoeltjen]

Progress dialog is most consistent with precedent (Import/Export)

May make sense to add platform support for this (perhaps in WindowManager?) such that plug-ins don't need to worry about re-implementing it every time