Add script to bump version numbers (rebased onto dev_5_0)


This is the same as gh-1463 but rebased onto dev_5_0.

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This Python script should simplify the creation of PRs bumping the version numbers before and after release. To test it, follow a typical release workflow

```
$ python tools/bump_maven_version.py 5.1.0-rc1
$ git diff
$ python tools/bump_maven_version.py 5.1.0
$ git diff
$ $ python tools/bump_maven_version.py 5.1.1-SNAPSHOT
$ git diff
```

First 2 commands should update the versions in all `pom.xml` files as well as `STABLE_VERSION` in `UpgradeChecker.java` while the last one (with SNAPSHOT) should update the versions in all `pom.xml` only.