Choose Lookback Period for Correlation Tool

Rather than defaulting based on frequency, give the user the ability to define their own lookback period.

This was requested by Brian Ridgeway at AAM $48k. I've also seen correlations used quite a bit with other wholesalers and know this will be useful.

Brian is comparing funds and trying to prove to an advisor they are not as closely correlated to the fund he is selling against. He would like to see a 3 year lookback, as the standard 120 day does not capture the point he is trying to get across.