Search across multiple polygons

jirikadlec2[CodePlex]
When searching across multiple polygons which are neighboring polygons -
try to union these polygons first (using DotSpatial topology function) and then search on the bounding box.

This should speed up the search, by reducing the number of PointInPolygon tests and reducing the number of HIS Central service calls

Start by locating the multi-polygon search entry point, the PointInPolygon checks, and the HIS Central service calls. Review how DotSpatial topology functions can union neighboring polygons before the bounding-box search; done means the search still returns the expected results with fewer point-in-polygon tests and service calls.

Written by the indexing model from the issue text.