Java CC review: Address findings

At the time this issue was created, we have:
- around 122 issues detected by Sonar - need to be reduced constantly
- Unit test coverage is about 35%, need to be increased
- fake properties in gradle.properties file, that will influence all local repos, need to remove them and use -P, --project-props instead
- check the usage of catching Throwables, and keep only where it is a must (catch only exceptions we handle, and exceptions those are necessary to catch)
- remove checkstyle supression on method names (that allows underscores)

Start by reviewing the Sonar findings, unit-test coverage, gradle.properties, Throwable catches, and the checkstyle suppression mentioned in the issue. Done means the applicable findings are reduced, coverage is increased, fake properties are removed, catches are narrowed where appropriate, and the method-name suppression is removed.

Written by the indexing model from the issue text.