Implement StatFunction interface

[magicDGS]

In addition, it adds:

• General utility classes: BinaryPredicate and RelationalOperator
• Sub-interfaces for single reads or pair-end reads
• Implementation for counter of indels/softclips (single read)
• Implementation for counter of integer tag w.r.t. threshold (pair reads)

Closes #438

[codecov[bot]]

Codecov Report

Merging #446 into master will decrease coverage by 0.035%. The diff coverage is 92.308%.

@@              Coverage Diff               @@
##             master      #446       +/-   ##
==============================================
- Coverage     93.23%   93.195%   -0.035%     
- Complexity      833       894       +61     
==============================================
  Files            81        89        +8     
  Lines          2319      2410       +91     
  Branches        254       259        +5     
==============================================
+ Hits           2162      2246       +84     
- Misses          120       126        +6     
- Partials         37        38        +1

Impacted Files	Coverage Δ	Complexity Δ
...ools/utils/read/stats/PairEndReadStatFunction.java	100% <100%> (ø)	2 <2> (?)
...ils/read/stats/pairstat/PairIntegerTagCounter.java	100% <100%> (ø)	10 <10> (?)
.../readtools/utils/read/stats/StatFunctionUtils.java	100% <100%> (ø)	2 <2> (?)
...ils/read/stats/singlestat/ContainIndelCounter.java	50% <50%> (ø)	2 <2> (?)
.../read/stats/singlestat/ContainSoftclipCounter.java	50% <50%> (ø)	3 <3> (?)
...icdgs/readtools/utils/read/stats/StatFunction.java	66.667% <66.667%> (ø)	3 <3> (?)
...icdgs/readtools/utils/math/RelationalOperator.java	92.857% <92.857%> (ø)	16 <16> (?)
...read/stats/pairstat/PairIntegerTagListCounter.java	97.826% <97.826%> (ø)	23 <23> (?)
... and 6 more