Assorted metadata/tile parsing fixes

To test, verify that the following tickets are now resolved:

https://trac.openmicroscopy.org.uk/ome/ticket/11087
https://trac.openmicroscopy.org.uk/ome/ticket/10796
https://trac.openmicroscopy.org.uk/ome/ticket/11683
https://trac.openmicroscopy.org.uk/ome/ticket/11867

This should be rebased onto dev_5_0.