Significantly reworked the get_intersection_point function. Now this function...

Significantly reworked the get_intersection_point function. Now this function with move the intersection point down stream one cell, which is more likely to be one a burned stream cell. Also bumped down the snap flowline buffer of the on_flowline function to 17.5m. Lastly, and most importantly, fixed a problem with the pyflwdir delineations; sometimes multiple polygons are returned from a delineation and originally only the first polygon was passed along. This happened in catchments with 'hanging cell' as these would be vectorized into their own polygons. Now the delineation polygons are merged together before being passed along.