Project: Xcode wibble.

Let Xcode perform recommended changes. Warnings--.
Frameworks: Updated to RW6 variants.
Project: New plug-in extension.

Use the new "rapidweaverplugin" extension so that RW6 recognizes us.
Frameworks: Update Sparkle to remove code signature.
RMSSamplePlugin imports RWKit.
Sparkle: Refactor framework loading.

Includes an updated method to return any load errors to the caller.
Sparkle: Handle case where Sparkle returns nil.

Specifically handles the case where the framework is successfully
loaded but returns nil when called. Makes it clear as to where the
problem lies, here or in the Sparkle framework.
Sparkle: Update call site.

Now uses the updated API to capture errors and log them.
Project: Remove Install Script phase.

Script needs to be updated to copy (not link) into the proper sandbox
container.
Merge branch 'rw6-ready'