Access to samples and sample editing

[git-moss]

There are 2 cases:

1. Sample in clip: Clip.getSample()
2. Samples in the Sampler: Device.hasSamples(), Device.getSample(index)

Required API features:

• get sample waveform data for drawing -> requires a window into the sample with a zoom factor -> functions for setting the start, end and zoom factor (incl. vertical zoom factor)
• Set start, end, loop of sample (could be similar to the API for clips)
• Set stretch mode, set stretch factor
• Slice to drum machine, slice to sampler (with parameters like in the dialogs)