The missing CoreFoundation include was causing issues when building
VST3 plugin-hosts.

Projucer:  Add all format-specific plug-in files in juce_audio_plugin_client to correct targets in Visual Studio

Fixed some incorrect documentation examples for the Rectangle::removeFromRight() and ::removeFromBottom() methods

macOS:  Render OpenGL frames on ThreadPoolJob instead of directly on the CVDisplayLink thread to avoid a deadlock

This change gives projects more flexibility to e.g. pre-build
juce_audio_plugin_client into a staticlib and to reuse it in several
targets.