refactored contentType of DTTextAttachment into a class cluster
corrected display size problem on new DTTextAttachmentImage

only having an image should set the originalSize
Switched inline image drawing to DTTextAttachmentDrawing protocol
Updated HTML persistence of <object> elements
Added DTTextAttachmentHTMLPersistence
removed @optional, if subclasses of DTTextAttachment are tagged with the protocol then you have to implement the method.
cleaned up registration of custom classes
moved childNodes to object subclass
fixed multiple calling of initialize in class clusters. Implemented custom text attachment support
Merge branch 'master' into od_attachment_cluster
Renamed all members of DTHTMLElement class cluster to have the specialization as prefix.
Renamed members of DTTextAttachment class cluster to use prefix for specialization.
further renaming effects of DTTextAttachment class cluster change
two more that refactor has missed
Cleanup renamed stuff
Updates for DTCoreText 1.5 attachment class cluster
Merge branch 'od_attachment_cluster' into develop
added unit tests for #402
added comment
removed one unit test, we ignore invalid colors