LUI-96 Add github PR integration for test coverage

• add jacoco maven plugin for generating coverage reports
• add coveralls maven plugin to send jacoco reports to coveralls.io
• add travis after_success command to send jacoco reports to coveralls.io after successful builds
• jacoco and coverals are configured in root pom pluginmanagement
• jacoco only generates coverage for omod/ for now since there are no tests in api/

see https://issues.openmrs.org/browse/LUI-96

TRY: you can locally get the coverage report with:

mvn clean install jacoco:report

should run tests, prepare jacoco and generate omod/target/site/jacoco with an index.html where you can see the unit test coverage report.

TODO: hopefully after the first run on travis CI the project will show up at: https://coveralls.io/github/openmrs/openmrs-module-legacyui

the maven coveralls plugin states that if using travis CI no further config is needed: https://github.com/trautonen/coveralls-maven-plugin#configuration

unfortunately I cant remember if I had to add the project on coveralls for the radiology module. see https://coveralls.io/github/openmrs/openmrs-module-radiology?branch=master

final TODO, add the badge to this repo ;) this needs to be shown, since this repo misses loooots of tests! 😨