Copy for selected block and inline leaf nodes

[mweiss]

Currently, if you try to copy an inline of block leaf without selecting it as part of a range selection, it will not update the text/html clipboard data. This is because native browser copy-paste behavior will not copy anything for a caret selection. Perhaps can be fixed several ways: by making a selected block leaf or inline leaf a range selection via focus and anchor offsets as boundary points, having a custom clipboard for selected leaf nodes, or by setting the clipboard data on copy events. However I haven't tried any of these methods out to see if they're viable.