Add code coverage report generation to Alitheia core.

Add code coverage generation of tests in Alitheia Core. Might be helpful to merge for others to use during test generation.

The coverage reports will be generated at the end of the `mvn test` run in the `alitheia/core/target/coverage-reports/` directory.

Note that this coverage is only being added to the `alitheia/core/pom.xml` file. This is done to quickly run tests on the core subset of alitheia without testing the rest. Is there a way to load the settings from the global `pom.xml` file?