Fix code indentation, was a mix of spaces and tabs
Delete duplicate of SelectionBasedTextOperationCmd

Seems this class was not used anywhere, leading to confusion.
Clean up visual tests

Replace checkCommand with checkLeavingCommand, simply check the final
editor mode instead of using Mockito, don't switch to visual when
a test already put us in one of the visual modes.
Add test for selection side switching
Fix caret position for TempVisual to Insert switch

Most operations work fine when invoked from Temp visual mode, but
pasting while in this mode would put the cursor one character back.

This commit overrides this behaviour by making a new PasteOperation
instance triggering the right action, then overriding the binding in
TempVisualMode. See included test code for results.

Fixes #400.