OL3 Support about maputnik

[lukasmartinelli]

Wow that was easy. Replaced Mapbox GL with OL3 in 5faa971.

Obviously far from perfect - but by just calling a new map render each time
we can already do some basic editing... this is really doable with OL3. Very excited.

/cc @jj0hns0n @klokan

GIF is using OL3 with the Basic style and OSM2VectorTiles CDN.

[jj0hns0n]

:)

[lukasmartinelli]

Should OL3 support be alongside Mapbox GL or should it be compiled separately.
I don't like to ship huge JavaScript files with two renderes but I think even worse is having
two versions of Maputnik.

If both render engines are shiped then
in the editor one would then be able to choose the renderer for the style.

If OL3 is included in that way I ensure during development that it will work in both renderers and is not just an afterthought.

[pathmapper]

Experimental OpenLayers support was added again in #397.