Keyboard shortcuts for reviewing comments

[bironran]

Some keyboard shortcuts for reviewing comments are sorely missing:

1. When in comment editor, accept/reply e.g. Ctrl-Enter and cancel e.g. Esc.
2. When in comment editor or comments list, goto code location e.g. F4 (goto source).
3. When in code editor, jump to comment for this line. Maybe should be default behavior for new comment task?
4. When in code editor, go to next/previous file in the MR e.g. Alt-Right/Alt-Left like in diff editor / maybe Alt-Down/Alt-Up because the file list is vertical? Also F7/Shift-F7 when on last diff / when on first diff like diff editor)
5. When in comment list, ability to scroll to to source on changing current selection, especially using keyboard up/down (like project pane).