Switched from cobertura to JaCoCo for coverage

[rianniello]

• A coverage report is generated and displayed on each gradle build, making it easier to keep an eye on coverage.

Example output:

------------------ Code Coverage -----------------------
- instruction coverage rate is: 100.0%, minimum is 85%
- branch coverage rate is: 100.0%, minimum is 85%
- line coverage rate is: 100.0%, minimum is 85%
- complexity coverage rate is: 100.0%, minimum is 85%
- method coverage rate is: 100.0%, minimum is 85%
- class coverage rate is: 100.0%, minimum is 85%
--------------------------------------------------------

• The build breaks if minimum coverage isn't met. This will be beneficial for PRs.
• I have set minimum coverage to 85% for all metrics. This is to be reviewed.
• JaCoCo can be integrated with coveralls which we may use in the future.

[smangelsdorf]

85% minimum coverage? Pfft...