fix macOS build (following Projucer changes made in Windows, which removed /Applications/JUCE/modules from its headers). move JUCE headers under source control, so that Windows and macOS can both build against same version of JUCE. remove AUv3 target (I think it's an iOS thing, so it will never work with this macOS fluidsynth dylib).

modules/juce_blocks_basics/README.txt

@@ -0,0 +1,9 @@
+
+This is a JUCE module which discovers any connected BLOCKS devices and provides low-level
+access to their physical properties.
+
+Its job is to provide:
+- topology and status information about the list of connected devices
+- callbacks for touch events, control button presses and rotary dial movements
+- simple control over individual LEDs
+- optional rule-based virtual device aggregation functionality