Submitter: support error callbacks

This commit introduces error callbacks to the submitter. This can be
added along all the other parameters when a new request is queued. If
the submitter needs a reset, the error callback of every element in the
queue is called.

This change is needed to deal with issue #598.
Interpolated node requester: handle failing node update

If the node update fails that is required for the last queue element, it is
retried three times before an error message is displayed to the user. This
message asks him/her to reload CATMAID due to an unrecoverable problem.

This deals with issue #598.