Refactored constructors of BEvent and added documentation

src/main/java/beamline/events/BEvent.java

src/main/java/beamline/sources/CSVLogSource.java

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

src/main/java/beamline/sources/StringTestSource.java

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

src/test/java/beamline/tests/AlgorithmTest.java

src/test/java/beamline/tests/EventTest.java

src/test/java/beamline/tests/FiltersTest.java

src/test/java/beamline/tests/MapperTest.java

src/test/java/beamline/tests/ResponsesTest.java