* support edit types based on edit widgets (adds qgis_gui dependency; fixes#12091)
* show null values (fixes#12114)
* only quote non-numeric non-null values in feature info
* fix crash on exit
* remove obsolete parser method and debug output
*Styled Layer Descriptor profile of the Web Map Service* : DescribeLayer
http://www.opengeospatial.org/standards/sld
Defining a user-defined style requires information about the features being
symbolized, or at least their feature/coverage type. Since user-defined styles
can be applied to a named layer, there needs to be a mechanism by which a
client can obtain feature/coverage-type information for a named layer. This is
another example of bridging the gap between the WMS concepts of layers and
styles and WFS/WCS concepts such as feature-type and coverage layer. To allow
this, a WMS may optionally support the DescribeLayer request.
DescribeLayer method has been thought to be a better approach than overloading
the WMS capabilities document even more.
For each named layer, the description should indicate if it is indeed based on
feature data and if so it should indicate the WFS/WCS (by a URL prefix) and
the feature/coverage types. Note that it is perfectly valid for a named layer
not to be describable in this way.
