Merge pull request #1810 from mattyb149/dev

[PDI-10610]: Moved INamespace inheritance to IMetaverseComponentDescriptor
Merge pull request #1813 from mattyb149/dev

[PDI-10610]: Added type to getChildNamespace()
[PDI-10610]: 	distinguish file extension from document type; add mime type.
Merge pull request #1817 from gretchiemoran/metaverse

[PDI-10610]: 	distinguish file extension from document type; add mime ty...
[PDI-10610]: Added IHasProperties for common key/value handling