Update release prepare command

Currently `mvn clean release:prepare` command does the next:
- Changes versions to necessary versions
- Makes uncommitted files `release.properties` and `pom.xml.releaseBackup`
- Creates an unsigned commit with the release
- Creates an unsigned commit with the next development version

Our flow requires that we update documentation files during the release and sign the commit that is why the `mvn clean release:prepare` should be changed a little bit.

My proposal is to create a script which executes `mvn clean release:prepare` and then does the next:
`git clean -df`
`git reset --hard HEAD~1`

So, that we would end up with only one commit which we will change with `git commit --amend -s` after making necessary doc changes.

Start by locating how the project invokes `mvn clean release:prepare` and where release documentation or scripts are maintained. Review the proposed `git clean -df` and `git reset --hard HEAD~1` sequence, then verify that the flow leaves one amendable release commit and supports the required documentation changes and signed commit.

Written by the indexing model from the issue text.