Adding or deleting an Assetstore leaves the web client it an odd state.

Fixes issue #265.  When you added or deleted an assetstore, the web client would not properly reflect what had occurred.  Subsequently setting the current assetstore would result in an error, though the task would be done properly.

Also, when you deleted the current assetstore, uploads would fail for lack of a current assetstore.  If another assetstore is available, automatically select the most recently created one.