respect preference state (#4468)

* When initializing the UI from prefs, fire an event to make sure dependent controls get updated.

Drive-by code cleanup -- enums are singletons; don't call enum.equals(), just use ==.

* Update changelog to document fix.

* Refactor enable/disable logic to its own method

* Revert CHANGELOG. Change checkbox disable/enable logic to use FX bind / observable.

* remove line which overrides the preference for updateTimeStamp

src/main/java/org/jabref/gui/preferences/GeneralTab.java

@@ -139,7 +139,6 @@ public void setValues() {
         useTimeStamp.setSelected(prefs.getBoolean(JabRefPreferences.USE_TIME_STAMP));
         overwriteTimeStamp.setSelected(prefs.getBoolean(JabRefPreferences.OVERWRITE_TIME_STAMP));
         updateTimeStamp.setSelected(prefs.getBoolean(JabRefPreferences.UPDATE_TIMESTAMP));
-        updateTimeStamp.setSelected(useTimeStamp.isSelected());
         enforceLegalKeys.setSelected(prefs.getBoolean(JabRefPreferences.ENFORCE_LEGAL_BIBTEX_KEY));
         shouldCollectTelemetry.setSelected(prefs.shouldCollectTelemetry());
         memoryStick.setSelected(prefs.getBoolean(JabRefPreferences.MEMORY_STICK_MODE));