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If there were multiple features of the same type in a GeoJSON file and
the file did not include names for the components, one would receive
multiple components with the same name (e.g., LineString1). LineString
processing was also broken, resulting in a coordinate string without
values. Setting the Source to None... would remove the components but
not clear the features off the map.

This commit addresses three changes:

1. Refactors how naming of map features is handled during the loading
   of GeoJSON into a MockFeatureCollection so that each component has a
   unique name.
2. It corrects handling of LineString coordinates when the line string
   is not part of a MultiLineString construct.
3. It cleans up how features are removed when a feature collection is
   cleared.

Change-Id: Iccbcab65989169ab730239b8915b62ca6b6f636c