AUV fix for auv viewer

 * removed st_makevalid(geom) in both images and tracks views. This
   slowed down considerably geoserver and the auv_viewer
 * created a postgres function instead to look for polygons of images
   which are too small and are in fact points, and then expand the
   polygons using st_buffer using an infinitesimal increase.
Merge pull request #112 from aodn/auvViewerViewsfix

AUV fix for auv viewer