Tempo synced Delay Plugin

I have been working on a native delay plugin. It makes use of the TempoSycnKnob for both the delay time, and the lfo time.

first pull request ever !!! please let me know if I have done anything  wrong..
Hmm. You're setting a maximum delay of 20 sec at 192k samplerate... but our maximum samplerate is currently 8x192k (oversampling). 

So maybe it'd be best to set the maximum length according to the samplerate and change it when samplerate changes. This way we also don't use up more memory than we need.