Close document in channels perspective when starting to fully-edit it

Symmetric to CHANNELMGR-1017, when a document is opened (for viewing or editing) in the content perspective, if that document is currently open for Visual Editing in the channel manager, the right side panel of the channel manager should be closed without any changes to the document's workflow. If the right side panel's editor form was dirty (pending changes), these changes are lost*.

• when switching from Visual Editing to the content perspective using the Publish or Full Editor buttons, any pending changes would be saved upon leaving the channel manager, so you can only lose changes when using the perspective tab to navigate to the content perspective. Also, once we've implemented auto-saving for PSP2, chances of having unsaved pending changes in the channel manager will be even lower.