TrendAnalysis should raise an error for unknown filters

[mdeceglie]

Is your feature request related to a problem? Please describe.
TrendAnalysis checks its attribute filter_params (and filter_params_aggregated) to control filtering. These attributes are dicts, where the keys are the names of the filter functions to use. If an unknown filter function name is supplied, TrendAnalysis quietly ignores it.

Describe the solution you'd like
Raise an error