Support Page Model API with version in the URL as path info

The currently PMA URL is currently something like

/site/api/[project-name]/page

A different version of the PMA can be requested via the 'Accept-Version' header.

However, according [1] and [2], the best practice is to have the version in the path info. For the PMA, the most logical part in the pathInfo to support this is most likely this:

/site/api/1.0/[channel-name]/page
/site/api/1.1/[channel-name]/page
/site/api/2.0/[channel-name]/page

Next to this, we also need to decide whether the PMA will become available below

/site/api/1.0/[channel-name]/page

or rather below

/site/api/1.0/page/[channel-name]

Since I expect that next to 'page' for PMA we also need to support 'content' to serve a single document in Page Model API format, I prefer :

/site/api/1.0/[channel-name]/page

which gives room to

/site/api/1.0/[channel-name]/content

Also note that supporting '/[channel-name]/page' instead of '/page/[channel-name]' is much easier in the current HST. I am not sure how much time the alternative would take to implement but I think considerable.

The 5 story points is only for moving the version into the pathInfo

[1] https://ci-xm.corp.bloomreach.com/static-content/api-guidelines/
[2] https://issues.onehippo.com/browse/BRGAC-4