[code-reflection] Integrated: Mavenized backend building

[Gary Frost]

Mostly changing backend java layout from 'backends/MyBackend/java/' to mavens preferred `backends/MyBackend/src/main/java.

The build can now be controlled form the top. 

mvn clean compile jar:jar

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Commit messages:
 - Mavenized backend building - chmod -x cmake.bash
 - Mavenized backend building

Changes: https://git.openjdk.org/babylon/pull/120/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=120&range=00
  Stats: 1031 lines in 59 files changed: 620 ins; 325 del; 86 mod
  Patch: https://git.openjdk.org/babylon/pull/120.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/120/head:pull/120

PR: https://git.openjdk.org/babylon/pull/120