Implement mock "delineate watershed" tool.
Implement mock "delineate watershed" tool.

* When the user selects one of the delineate watershed methods,
generate a random polygon centered where the user clicked. The
shape occasionally looks vaguely like a watershed. This is
temporary until there is support for generating watershed boundaries.

Refs #300

project-icp/bee-pollinator-app,mmcfarland/model-my-watershed,lliss/model-my-watershed,kdeloach/model-my-watershed,mmcfarland/model-my-watershed,kdeloach/model-my-watershed,lliss/model-my-watershed,lliss/model-my-watershed,lliss/model-my-watershed,WikiWatershed/model-my-watershed,mmcfarland/model-my-watershed,kdeloach/model-my-watershed,mmcfarland/model-my-watershed,lliss/model-my-watershed,project-icp/bee-pollinator-app,project-icp/bee-pollinator-app,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,mmcfarland/model-my-watershed,kdeloach/model-my-watershed,kdeloach/model-my-watershed,project-icp/bee-pollinator-app,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed