[Tagging] A second step towards bringing the wiki and tool support closer together

[Cartinus]

Data is grouped in layers.
These layers get their data from a datasource.
This data is styled with styles.

Some styles contain a filter expression, to restrict the application of that 
style to only a limited number of items within the layer.

Other styles simply apply to all the data within the layer..


The layer for turning circles has a datasource which only returns highway 
points with the tag value "turning_circle". So the style applied there 
doesn't need any filter.

The layers that paint the place labels and amenity icons have datasources that 
return data with multiple possible values for the place/amenity tag. So more 
selection is needed in the style applied there.


-- 
m.v.g.,
Cartinus