KT-3725 Maven pom files, in kotlin libraries, don't have The Central Repository requirements.

- Added required tags to parent pom.

- Added source and javadoc generator to all poms

- Replaced "build-helper-maven-plugin" by "maven-install-plugin"  to install the correct pom file alongside with artifacts.

A test release has been deployed to maven central to make sure artifacts are valid and deployable.