Add new scroll restoration helpers

[Jyrno42]

These are replacements for the scroll restoration behaviour in View.js. To use any of these make sure to call initSpaScroll() in your clientside entrypoint before rendering your application.

Note: The scroll restoration logic in view will be removed/disabled separately in another commit once the general direction is accepted as the path forward.

Also:

• Allow specifying behaviour in windowScroll. Behaviour now also defaults to smooth. To retain instant scroll set the value of the parameter to null.

[coveralls]

Coverage decreased (-3.0%) to 65.265% when pulling b5bd906a0b409e06f87b03f4e5d0b21a1c7e459a on Jyrno42-patch-1 into d61fd05586265102bf85502a353e9258625b5fb2 on master.

[Jyrno42]

Ignoring coverage, view module has no tests anyway.