title is mandatory for every Description
importers version 1.1
Merge latest importer changes. The Description model now has a mandatory title
attribute. Fixtures adapted to match.

Also made some (unfinished) changes to the BundleError exception so we will be
able to report a full error tree usefully. Currently, if the error is somewhere
within the bundle's sub-relations (i.e. on the Description), then the exception
won't show anything useful to figuring our that's wrong!

Conflicts:
	ehri-frames/src/main/java/eu/ehri/project/models/AuthorityDescription.java
	ehri-frames/src/main/java/eu/ehri/project/models/base/Description.java
	ehri-importers/src/main/java/eu/ehri/project/importers/EaImporter.java
	ehri-importers/src/test/java/eu/ehri/project/importers/EacImporterTest.java