Better heuristic for inverting ranges in normalizeSelection
[sublime keymap] Add support for shift-alt-up/down
[sublime keymap] Fix coding style in 8eb523db08b80b0ff70728d9b71475cadb2bcf93

Also, wrap the command in an operation and use the head rather than
the anchor of the selections.
[sublime keymap] Fix shift-ctrl-d binding

It should duplicate for every selection, and for non-empty selections
only duplicate the selected text.