Sync record audio with metronome

[ffont]

Currently audio can be recorded by clicking on the "record" button. The audio recording starts right after clicking the button and stops when clicking again. There should be an option to enable syncing the recording with the metronome and potentially specifying a number of bars to be recorded. Then once hitting the record button it would wait until the next beat to start recording. This way it would be easy to export loops created with Freesound Explorer.