permit to use TMS layers as baselayers

[landry]

So far we can only use WMS layers as baselayers in mapViewer.. this is great but slow with complex map/photo layers. For performance reasons it'd be great if we could use TMS layers too with fixed scales, and then also decide the scale/unit of the whole ol map.

Maybe smth like

<mapViewer>
<scales>x,y,z</scales>
<units>m</units>
<layers>
<layer type=TMS server=tmsurl options="{ layername: 'ortho', type: 'jpeg'}"/>
<layer type=WMS server=wmsurl params="{ layername: 'commune', format: 'image/png'}" options="{isBaseLayer:false}"/>
<layers>
</mapViewer>

If there's any interest into that enhancement, maybe i can try to implement it...

[landry]

Find attached a conceptual diff (untested, but you get the idea) to implement units/scales and tmslayer config keys. It includes examples/documentation. To be discussed:

• merge it with <layer> key so that you only pass one array to init(), and add a 'type' attribute as proposed previously, defaulting to WMS to avoid breaking existing setups ? That way, you only need to make the difference between TMS/WMS when creating ol layers
• set default array of scales in case it's not used ?
• use it too in ol_minimap.js ? in extentMap.js ? One could debate the usefulness of multiple layers in both of them, whereas multiple base layers make sense in the main map viewer.