Per #1761, updates to Simple_Node::set_perc() to handle variable freq…

…uency bias amounts.

Changes include:
- Reverting the formatting of this back to how it originally was in the develop branch. In general, just match the formatting of the existing file, so as the minimize the number of difference lines.
- Add logic to adjust the percentile to be found based on the requested FBIAS value. Multiplying or dividing the percentile by the FBIAS value depends on the inequality type and whether we're bias adjusting the forecast or observation data.
- Adjust the log messages slightly.

Please be aware that I'm not totally confident in these changes. They warrant much more testing. This logic is very, very confusing.