Spotless gradle plugin

Added

This MR adds spotless to the gradle build using a configuration file called eclipse-formatter.xml. The following choices were made:

1. Parameters in method signatures and constructors are block-aligned on the column after the opening parenthesis. This is for better readability most prominently in Controller classes.
2. Tabs are used for indentation per Otto's request.
3. JavaDoc parameter and return value documentation is block aligned after the widest parameter name.
4. Any other formatting decisions are based on a template formatting available in Eclipse IDE as 'Java Conventions [Built-in]'

To-do

• @otto Should take a look at whether the gitlab build and tests have to be adjusted for this.
• To have license formatting on I changed the LICENSE.header file, will this interfere with license checking already in the Gradle pipeline?