Disable layer when REST upload contains layer that cannot be completely configured

As discussed on the mailing list, this patch would change the behavior of the RESTConfig file upload endpoint. The current behavior is, after an upload whose configuration cannot be completed (for example, the native projection and therefore the lat/long bounding box cannot be determined) the layer is left in the catalog, warts and all. The erroneous data doesn't cause an error at upload time, but the next WMS GetCapabilities request will throw an exception due to the null fields.

With this proposed change, the layer would simply have the 'enabled' bit set to false so that uploaders can switch it to false at the same time they complete the configuration (either via rest or through the web interface).