Build proof of concept for Mac OS audio recorder

# 1st iteration: ## Proof of concept I want to build a native cocoa macosx audio recorder, but would need to see first a proof of concept, which will serve as the first iteration of the software to be built. As a reference Piezo from Rogue Amoeba. I will also compare cpu usage versus it. ## Future collaboration If i see that it can work the way i want to use it in the future, we will iterate again until complete application. ## Deliverables - Please start a new git repository for this code and deliver this repository, as well as instructions to recompile the software with xcode. - Clean code, with comments - Please mention any 3rd party libraries or external code that you used and links, to check licensing terms. ## Features _(Letters) are related to components on the attached mockup_ - Single window with record on/off button, radiobutton output/input/both (R), select application button or global recording (Q). - Record audio like Piezo or AudioHijack (output and/or input) - Record audio globally or per application (Q) - Cpu usage < Piezo - Display live dB level and nb of seconds below 60dB (text label is fine) (D,E) ## Mockup _see attached file_