Move JDBC drivers to a shared location

[hansva]

In this PR all JDBC drivers that we include in our distribution have been moved to lib/jdbc.

The Variable that can be used to add external JDBC drivers has been changed to HOP_SHARED_JDBC_FOLDERS and accepts a comma separated list of folders.

The relevant documentation changes have happend

Added the option for transforms/actions to also load the JDBC driver folder if needed (mainly for bulkloaders)
Grouped the classloaders of the bulkloaders and their relevant Database types to avoid having the JDBC drivers in separate classloaders.

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Run mvn clean install apache-rat:check to make sure basic checks pass. A more thorough check will be performed on your pull request automatically.
• If you have a group of commits related to the same change, please squash your commits into one and force push your branch using git rebase -i.
• Mention the appropriate issue in your description (for example: addresses #123), if applicable.

To make clear that you license your contribution under the Apache License Version 2.0, January 2004
you have to acknowledge this by using the following check-box.

• I hereby declare this contribution to be licensed under the Apache License Version 2.0, January 2004
• In any other case, please file an Apache Individual Contributor License Agreement.