Merge pull request #1869 from rcordovano/6217-refactor-art-attr-JSON-utils

.../java/src/org/sleuthkit/datamodel/TimelineEventTypes.java

...euthkit/datamodel/blackboardutils/GeoArtifactsHelper.java

...l/blackboardutils/attributes/BlackboardAttributeUtil.java

...el/blackboardutils/attributes/BlackboardJsonAttrUtil.java

.../datamodel/blackboardutils/attributes/GeoTrackPoints.java

...it/datamodel/blackboardutils/attributes/GeoWaypoints.java

...amodel/blackboardutils/attributes/MessageAttachments.java

...del/blackboardutils/attributes/TskGeoTrackpointsUtil.java

...model/blackboardutils/attributes/TskGeoWaypointsUtil.java