pass maxFramesToRender to DSPBase::init

[wtholliday]

Is your feature request related to a problem? Please describe.

An AudioUnit will often need to know the maximum buffer size that will be requested for rendering. AudioKit doesn't provide this.

Describe the solution you'd like

maxFramesToRender should be passed to DSPBase::init.

Describe alternatives you've considered

This information could possibly be grabbed from the size of the output buffers but that is inelegant.

Are there examples for this somewhere in the code?