Restore MapModal select rectangle/bounds functionality.

[landonreed]

Issue by landonreed Thursday Aug 23, 2018 at 17:48 GMT Originally opened as https://github.com/catalogueglobal/datatools-ui/issues/238

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This feature was removed due to an issue with react-leaflet-draw. However, that implementation was probably overly complicated and could be implemented with simple draggable markers and rendering a rectangle representing the chosen bounds.

Previous implementation can be seen (mostly commented out) here.