* Deleting a PlaceDataSource is now possible; here's the missing template file

* When saving a PlaceDataSource and there are errors (e.g. blank option field) the changes are still saved; these errors are reported but are non-fatal. This gets out of a chicken-and-egg problem of (for example) a bad URL not fetching fields, and bad fields preventing you from saving the corrected URL.

* PlaceDataSource now has the listFields() instance method, and "option" fields now support _isfield_ setting. In the Place Data Source admin panels, this forces these fields to be a selected field from the list.

* PlaceDataSource and EventDataSource now have a _on_by_default_ setting, to set whether they're checked/visible when the Map/Calendar pages first load.

* Admin panel for Place DataSources: now uses circular icons to match those on the Map

* PlaceDataSource admin panels now have a "warning" variable, to present the warning in a red box; great for when the data source isn't working, e.g. malformed URL

* PlaceDataSource_ArcGISREST now allows https:// URLs