Add back in recording mode

[bboettcher3]

I took out the "record your own audio" mode in v1.0.0, but it should be added back in! Most of the code is still there, maybe some is commented out.. anyway, look in Source/DSP/AudioRecorder.h/.cpp (should be working as expected) and Source/PluginEditor.cpp (where the commented-out code would be) to re-enable it. We'll need a new microphone png for the button as well :)