Fix bad constructor bug. Add possibility to show mouse position.
Fix bad constructor bug. Add possibility to show mouse position.

hms-dbmi/higlass,hms-dbmi/4DN_matrix-viewer,hms-dbmi/4DN_matrix-viewer,hms-dbmi/higlass,hms-dbmi/4DN_matrix-viewer,hms-dbmi/higlass,hms-dbmi/higlass