simplified ul_confidence_bounds

* precomputed values are now a table instead of elifs
* two possible returns
* cyclomatic complexity down from a score of 60 to 8
added credit
simplified entropy check
rework of filter_alignment.apply_lane_mask_and_gap_filter

* no more temporary files
* cyclomatic complexity down from 34 to 9
* much smaller method
Merge pull request #1231 from wasade/cc_fixes

Reducing complex methods