add counter store

[bfulton]

Fixes #19

@kbarrette @jazzdan

This modifies LongLookup to support replacing long values associated with keys, then uses that to add a new CounterStore, also available through the Uppend builder pattern.

[codecov-io]

Codecov Report

Merging #37 into master will increase coverage by 5.52%.
The diff coverage is 76.22%.

@@             Coverage Diff              @@
##             master      #37      +/-   ##
============================================
+ Coverage     57.64%   63.17%   +5.52%     
- Complexity      193      233      +40     
============================================
  Files            28       30       +2     
  Lines          1197     1287      +90     
  Branches        113      118       +5     
============================================
+ Hits            690      813     +123     
+ Misses          432      397      -35     
- Partials         75       77       +2

Impacted Files	Coverage Δ	Complexity Δ
...va/com/upserve/uppend/cli/benchmark/Benchmark.java	0% <0%> (ø)	0 <0> (ø)	⬇️
src/main/java/com/upserve/uppend/Uppend.java	73.33% <100%> (+19.48%)	6 <3> (+3)	⬆️
...va/com/upserve/uppend/FileCounterStoreBuilder.java	62.5% <62.5%> (ø)	5 <5> (?)
...ain/java/com/upserve/uppend/lookup/LookupData.java	72.88% <66.66%> (+0.27%)	23 <3> (+4)	⬆️
...main/java/com/upserve/uppend/FileCounterStore.java	88.88% <88.88%> (ø)	13 <13> (?)
...ain/java/com/upserve/uppend/lookup/LongLookup.java	75.3% <88.88%> (+9.7%)	39 <6> (+5)	⬆️
...n/java/com/upserve/uppend/FileAppendOnlyStore.java	81.69% <0%> (+8.45%)	15% <0%> (+1%)	⬆️
... and 4 more

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