Added parameterized support for isolated/non-isolated undo/redo
commands. Previously, undo/redo was always performed in an isolated
manner, which meant side effect weren't provoked. This made sense in a
global history context. In a local history context, not so much; here
side-effects are welcomed, as models are now considered more separete
only connected via bindings. Therefore, the current value for undo/redo
is non-isolated.

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>