Remove unused __handledByCommandRegistry property
Add workspace commands via command registry again

Now that legacy jQuery command listeners are properly integrated with
the command registry, these commands can be moved back.
Add TextEditorElement and make TextEditorView a wrapper around it

This is the next step on converting all internal views to custom
elements instead of using SpacePen. The TextEditorElement instances
are associated with ::__spacePenView fields that are used for supporting
legacy access paths via atom.workspaceView.
Destroy model if TextEditorView is explicitly removed for compatibility
Assign attributes passed to TextEditorView constructor
Update settings-view to fix specs
Null guard ::element in TextEditorView::component synthetic property
Update wrap-guide to fix specs
Forward .abortKeyBinding() on CommandRegistry events to original event
Move editor commands to global command registry
Add text-editor-element-spec and fix handling of focus and attributes
Fix checkout-head-revision command