Abode feature result suggestions

[abodeuis]

This PR is on top of the first pull request that contained bug fixes (#23). These are my suggestions for improving the usability of the polygon feature schema. Notes on changes are as follows:

• All of the polygon map unit metadata fields have been moved into a single class PolygonLegend.
• The polygon segmentation data has been condensed into a single class PolygonSegmentation.
• PolygonLegendAndFeatureResult has been renamed to PolygonMapUnit and now contains a PolygonLegend and a List of PolygonSegmentations.
• The Provence of a result is defined by ModelProvenance which is now tied in at PolygonLegend and PolygonSegmentation as opposed to before when it was at an individual polygon level and not at all for legend data.
• Removed Georeferencing data from polygon data. One of the big reasons to change to this format was to decouple georeferencing from segmentation. All results should be in image coords space and independent of any georeferencing.
• Removed the old MapUnit Fields. I don't believe that any group produces that information and don't even think that a lot of that information is even contained in the map.
• Removed internal ids from sub-fields.

These are the changes I would like to discuss on Monday. I will also note that I have only made changed to polygon features. If the changes are accepted there can discuss following a consistent format in the line and point results.

[abodeuis]

Add CRS field back defaulted to CriticalMAAS:Pixel, CDR_Projection_id.

[abodeuis]

add model for polygon in polygon segmentation