Add PreBinner

[ffreyer]

PreBinner is a wrapper for another binner which averages values pushed to it over a certain range and then forwards those averages to the wrapped binner. Essentially it acts like one binning level in LogBinner, except that the number of values that are averaged can be adjusted.

The idea of this is to allow skipping early/low binning levels to reduce the amount storage that is used. This is essentially an alternative to skipping data (i.e. only pushing every N-th value)

• [x] Implementation
• [x] Tests
• [x] Docs