Ensure that QuickStrip stores only application-specific terms scoped to applications

Following discussion with Gregg yesterday, we have determined that we need to ensure that preferences saved by the QuickStrip take only the following forms:

i) genuine application-specific terms scoped to applications
ii) common terms stored at top level

This implies that we discontinue the use and support for "common terms scoped within applications" that were introduced as a stopgap last spring as we had to suspend work on the MatchMaker.

This implies that we need to do the following:

a) Ensure that the MatchMaker, when encountering a common term at top level for which there exists a translation to an application, knows to activate those applications. We should review whatever limitations there were, including whether it was difficult to guard against activation of numerous unwanted applications, that stopped us doing this before
b) Adjust the QuickStrip so that it now writes these common terms (e.g. contrast and volume settings) to top level rather than to specific applications
c) Prepare a migration process that will rewrite any preference sets written to date by the QuickStrip in the old format by hoisting common terms to top level.