add option to control how history is updated

[mojavelinux]

• Use update option to only process inbound request from URL (no updates on navigation)
• Use history option to control whether history is maintained

[mojavelinux]

I've introduced two different controls.

The first, "update", controls whether the URL is updated after the page is loaded. If the value is false, the deck is advanced to the hash indicated by the URL, but does not continue to update on navigation. The default is to update the URL.

The second, "history" controls whether the history is overwritten on each slide change or whether the history is preserved. The default is to preserve the history. A value of false disables this behavior so that the history remains unchanged.