Create reusable module plotMarker.js, and refactor addTreeMode.js to use it
Allow changing plot position from plot detail page

* Hit "Edit" to edit the plot details, then hit "Move Tree" to change plot location

Use new features of inlineEditForm.js:
* Use returned Bacon property "isInEditModeProperty" to update UI as user enters/exits edit mode
* Use "onSaveBefore" callback to augment uploaded data with plot location (plot.geom)
* Use "onSaveSuccess" callback to redraw the map when location is updated

Also:
* update_plot_detail() now returns the geo rev hash (via update_plot_and_tree())