added memory of initial facts for linear tracker explanator

...a/fr/boreal/explanation/api/encoders/GSATEncoder_GRI.java

...pi/processors/AbstractExplanationsProcessor_GMUS_GRI.java

.../explanation/api/processors/ExplanationProcessor_GRI.java

...xplanation/kb_gri/encoders/AbstractGSATEncoder_KBGRI.java

...gri/explainers/AbstractStaticGRIBasedExplainer_KBGRI.java

...to_be_removed/GRI/sat4j/FactSupportMUSSat4JProcessor.java

.../tracker_gri/encoders/AbstractGSATEncoder_TrackerGRI.java

...xplainers/AbstractStaticGRIBasedExplainer_TrackerGRI.java