adds rcf ForecastLeadTimeBins, corrects misc. formatting (#601)

* adds rcf ForecastLeadTimeBins, corrects misc. formatting

* update docs and API formatting w.r.t ForecastLeadTimeBins

* adds staticmethod decorators to class methods

* refactors ForecastLeadTimeBins

* adds new tests for ForecastLeadTimeBins

* update tests

* adds additional input type support, support for mixed input types

---------

Co-authored-by: samlamont <sam.lamont@gmail.com>

Author: samland1116

docs/sphinx/user_guide/notebooks/08_adding_calculated_fields.ipynb

@@ -316,6 +316,7 @@
     "- NormalizedFlow\n",
     "- Seasons\n",
     "- ForecastLeadTime\n",
+    "- ForecastLeadTimeBins\n",
     "- ThresholdValueExceeded\n",
     "- DayOfYear\n",
     "\n",