Completed tests for XesLogSource and CSV, started working on MQTT

src/main/java/beamline/sources/BeamlineAbstractSource.java

src/main/java/beamline/sources/MQTTXesSource.java

src/main/java/beamline/sources/XesLogSource.java

src/test/java/beamline/tests/SourcesTest.java

src/test/resources/sources/source_2.xes