Add a function to find conspicuously-frequent integer values

Timeseries I analize often have certain values that appear very frequently and that should be dropped (e.g. sensor is saturated, data transmission errors caused repeated values, sensor has a certain output on error, etc...).

This Merge Request adds a function parmesan.processing.find_conspicuous_values to find these kinds of outliers.

Closes #4 (closed)