Add code formatter (java/angular)

[timonback]

As a contributor, I face the difficulty of learning the project specific style guide. I personally, like the approach to use a formatter, which applies the format to keep the project in a consistent style. Also, I do not have to think (as much) about formatting anymore. Running a gradle task should fix most intendation, line breaks, syntax issues.

In the past, I have used https://github.com/diffplug/spotless, which has IDE + gradle integration and formatting options for many languages, including java and typescript. I used Java/Eclipse and npm/prettier.

@stavshamir What do you think about integrating a code formatter? Do you have a preferred style?