Introduce Java API

[zouzias]

Introduce LuceneJavaRDD for Java users.

[codecov-io]

Codecov Report

Merging #137 into develop will decrease coverage by 2.1%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           develop     #137      +/-   ##
===========================================
- Coverage    77.37%   75.27%   -2.11%     
===========================================
  Files           33       34       +1     
  Lines          999     1007       +8     
  Branches        90       86       -4     
===========================================
- Hits           773      758      -15     
- Misses         226      249      +23

Impacted Files	Coverage Δ
...uzias/spark/lucenerdd/api/java/LuceneJavaRDD.scala	0% <0%> (ø)
.../zouzias/spark/lucenerdd/store/IndexStorable.scala	66.66% <0%> (-3.71%)	⬇️
...spark/lucenerdd/config/LuceneRDDConfigurable.scala	60.6% <0%> (-1.56%)	⬇️
...spark/lucenerdd/partition/LuceneRDDPartition.scala	88.73% <0%> (-0.31%)	⬇️
.../scala/org/zouzias/spark/lucenerdd/LuceneRDD.scala	87.5% <0%> (-0.12%)	⬇️
...ias/spark/lucenerdd/query/LuceneQueryHelpers.scala	94.82% <0%> (-0.09%)	⬇️
...in/scala/org/zouzias/spark/lucenerdd/package.scala	95% <0%> (+1.06%)	⬆️

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[almogtavor]

@zouzias Any reason why this didn't get merged yet?

[zouzias]

@zouzias Any reason why this didn't get merged yet?

The main reason is that it has not been fully tested yet. It is just a WIP.