Implement minscale/maxscale

[klassenjs]

Implement minscale/maxscale hints to disable layers (in the catalog?) that can't/shouldn't be rendered. (Also, should this be renamed min/maxscaledenom for GM3?)

This appears as a TODO in components/catalog/layer.js:

        // TODO: Check layer for minscale/maxscale against
        //       the mapView.
        // if(isOutOfScale(layer)) {
        //  layer_classes.push('out-of-scale');
        // }

[klassenjs]

PR: #345