documents: Split upload parameters out into GDataDocumentsUploadQuery

This new object currently only specifies the destination folder for an
upload (replacing the folder argument to
gdata_documents_service_upload_document_resumable()), but will in future
allow specifying things like the ‘convert’ and OCR parameters for uploads.

API additions:
 • GDataDocumentsUploadQuery and its methods

API breaks:
 • gdata_documents_service_upload_document_resumable()
(Note that this API hasn’t yet been in a libgdata release, so this isn’t
a real API break.)

Helps: https://bugzilla.gnome.org/show_bug.cgi?id=656971