[Feature] Filter the moving and fixed image prior to registration

[IgorTatarnikov]

brainreg preprocesses the images prior to registration by filtering. We should replicate this functionality.

This will need a toggle in the UI, maybe a checkbox right above the Run button labelled Filter Images.

[adamltyson]

Just FYI, this pre-processing should be made flexible. One of the issues with brainreg is that the filtering is great for 10um serial section 2p datasets, and less good for everything else.

[IgorTatarnikov]

Sounds good, we should expose the parameters to the user to set via the UI.

In the same vein I guess we should also expose different filtering strategies! I'm unsure of how to present this via the UI, should we curate a set of filtering strategies and have users pick from those, or should we expose the entire skimage.filters and let users construct their own pipeline?