[Feature Request]: User Defined Java Class: add a getDatabase method

### What would you like to happen?

Migration: https://issues.apache.org/jira/browse/HOP-3313

As a developer, it could be useful to get database connection in User Defined Java Class to perform some specific and short tasks. Considering that by using some internal objects it is possible to get a Database reference in that Transform it would be useful (the same it was made for other useful methods) and cleaner to provide a getDatabase method that very easily will provide a Database object reference to the user. That method could sit in the common use folder of the Code snippit folder.

### Issue Priority

Priority: 3

### Issue Component

Component: Transforms

Start with the User Defined Java Class transform and the common use folder of the Code snippet folder mentioned in the issue. Review how other useful methods expose internal objects and determine where a getDatabase method belongs; done means the transform provides users with a Database object reference for short tasks.

Written by the indexing model from the issue text.