Tidy up gradle.properties

[domdomegg]

Description (required)

Working towards fixing #1941, and generally improving code quality

Low priority, however I don't think these lines of these files will cause merge conflicts with any other PRs.

What changes did you make and why?

• Tidied up gradle.properties by grouping related properties
• Moved Kotlin version property from build.gradle to gradle.properties like all the other version properties
• Renamed some version properties so they are all consistently PACKAGE_NAME_VERSION

Did not change any versions in this PR so should be functionally identical

Tests performed (required)

All unit tests pass

Tested 2.9.0-debug-tidy-gradle-props~911bda1b4 (betaDebug) on Galaxy Nexus (emulator) with API level 28.

[codecov-io]

Codecov Report

Merging #2175 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #2175   +/-   ##
======================================
  Coverage    5.69%   5.69%           
======================================
  Files         233     233           
  Lines       11639   11639           
  Branches     1082    1082           
======================================
  Hits          663     663           
  Misses      10921   10921           
  Partials       55      55

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[maskaravivek]

A few people are having trouble with fresh clones. Am merging this to put it out for alpha users while #2289 gets merge ready.