This fixes the current forward implementation of Peirce Quincuncial proj to correctly flip/reflect out the southern hemisphere to four triangles, and rotate entire result to a square or diamond. (It there resolves the issues identified with pull request https://github.com/OSGeo/PROJ/pull/2230 , where southern hemisphere was wrongly projected over northern, and reverses the restriction to northern hemisphere introduced there). It also adds additional lateral projection of the hemispheres.

- This PR adds an optional parameter `+type` which allows selection of projection. The `+type=square` and `+type=diamond` types match in principle ESRI's twin implementations of square and diamond PQ projs. The **default** if not specified is `+type=diamond`.

- The previous behaviour restricted to the northern hemisphere can be reproduced using the `+type=nhemisphere`, though this is an edge case only.

- An additional `+type=horizontal` and `+type=vertical` rectangular lateral versions have been added that place each hemisphere side-by-side. This is primarily to allow creation of projections such as Greiger Triptychial, which also require the additional optional params `scrollx` or `scrolly` in order to shift parts of the projection from one side of the map to the other. 

- Additional documentation has been added to proj description, including quoting the usual meridian used in common usage of projection, and images showing the different types.

 - this bumps format_version of tinshift JSON to 1.1 for the new field
   fallback_strategy
 - the default behaviour without that field is retained
 - if fallback_strategy is set to "nearest_side", then points that do not fall
   into any of the triangles will be transformed according to the nearest
   triangle
 - if fallback_centroid is set to "nearest_side", then points that do not fall
   into any of the triangles will be transformed according to the triangle
   with the nearest centroid