Fix property removedProperties of ops.OdtDocument.signalMetadataUpdated

was passed as removedProperties.attributes: !string
instead of    removedProperties: !Array.<!string>

also
* reuse initial spec variable
* only deep clone opspec.setProperties, as removedProperties is cloned by
  opspec.removedProperties.attributes.split(',') already
Init removedPropertiesArray to null, is understood by OdfContainer.setMetadata
Remove dead code from ops.OpUpdateMetadata
Add gui.MetadataController
Merge pull request #608 from kossebau/metadataController

add gui.MetadataController (+related fixes)