Allow customizing blank lines between organized import groups

[liancheng]

This PR tries to address issue #140 and improve IntelliJ IDEA compatibility.

[codecov]

Codecov Report

Merging #142 (a05593b) into master (869e427) will increase coverage by 0.29%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #142      +/-   ##
==========================================
+ Coverage   90.90%   91.20%   +0.29%     
==========================================
  Files           4        4              
  Lines         242      250       +8     
  Branches       12        8       -4     
==========================================
+ Hits          220      228       +8     
  Misses         22       22              

Impacted Files	Coverage Δ
rules/src/main/scala/fix/ImportMatcher.scala	100.00% <100.00%> (ø)
rules/src/main/scala/fix/OrganizeImports.scala	96.34% <100.00%> (+0.06%)	⬆️
...les/src/main/scala/fix/OrganizeImportsConfig.scala	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 869e427...a05593b. Read the comment docs.