Fixed some wrong displayed error messages in the UI.
Did some minor cosmetic changes in SpotterServiceClient concerning
exception messages and removed not needed methods.

Changed responses of SpotterService to always contain some meaningful
error messages even when it's just the name of the exception thrown when
no more information was provided.

Change-Id: I582faf47e9e69be839caec70b40a7eafbfd3cd9e
Signed-off-by: DenisKnoepfle <denisknoepfle@gmx.de>