Adds branch coverage column

[MrG00dkat]

Adds branch coverage column for the job view. Also includes refactoring common column to an abstract class.

[centic9]

Thanks for this PR!

Are existing setups where the column is in use automatically migrated? If not, is it possible to automatically add the new LineCoverageColumn instead? Or would we need to keep a "Dummy" class in the old place to be compatible?

[MrG00dkat]

Thank you for your feedback!
The configuration of the column was lost on a version update. I haven´t found a way to migrate the column configuration to the new column name. A dummy column means, that I also must make a copy of the jelly files. So, I renamed the LineCoverageColumn back to his original name JaCoCoColumn. I think that is the best way. After that the update works fine without losing the column configuration.