Adding fact support explanation and tests

...r/boreal/explanation/explainers/FactSupportExplainer.java

.../fr/boreal/explanation/explainers/KBSupportExplainer.java

...anation/solving_enumerating/encoders/KBtoGSATEncoder.java

...enumerating/gmus_processors/FactSupportGMUSProcessor.java

...on/solving_enumerating/gmus_processors/GMUSProcessor.java

.../test/explanation/explainer/FactSupportExplainerTest.java

...lanation/solvingViaGMUS/FactSupportKBGSATEncoderTest.java

...oreal/test/explanation/solvingViaGMUS/GMUSSolverTest.java

...l/test/explanation/solvingViaGMUS/GMUSTranslatorTest.java

.../test/explanation/solvingViaGMUS/KBtoGSATEncoderTest.java