Rewrite page navigation using hooks

[olemartinorg]

We have these sagas currently:

1. updateCurrentViewSaga
2. calculatePageOrderAndMoveToNextPageSaga
3. findAndMoveToNextVisibleLayout
4. watchInitialCalculatePageOrderAndMoveToNextPageSaga

Number 2 and 4 should disappear with #1491, which leaves us with updateCurrentViewSaga, and the code in findAndMoveToNextVisibleLayout which fixes a problem caused by the fact that updateCurrentViewSaga moves to a specific page instead of mostly moving forwards/backwards through the page order.

The new code should prefer using separate methods for next/prev instead of jumping straight to a specific page, to avoid problems like those solved in findAndMoveToNextVisibleLayout whenever possible.

Proposed solution:

• We lift the process task id to the url, and allow the users to navigate to an arbitrary step in the process model.
• Browser-back between process steps should show read-only/generic error message.
• We lift the current page of a process step to the url, and allow the users to navigate to arbitrary pages in the current process step.
• In the case where a user navigates to a task which is not the current task in the process engine, we show a generic page, which explains that this page is not editable. This page will also include a button to navigate to the first page of the current task.

Out of scope:

• Creating a read-only view of the current page if the user navigates to a process step which is not the current step in the process.
• Creating process-next buttons that can never be rendered in the read-only view. Moving the process along to the next step should be impossible from a step that is not the current step in the process.
• We should implement a button that can navigate to previous process step (with the help of process.next if defined in the process model).

Related issue(s):

• Fixing inconsistent prev/next navigation buttons #1446
• Page navigation doesn't change focus to top of form when using NVDA (WCAG 1.3.2) #1408
• #1658

[RonnyB71]

Based on the assumption that pageOrder will be removed and replaced with expressions.