use with ArcGIS feature server requests
Some servers are locked down to only allow requests with a specific
referer URL - this allows us to open them in QGIS (but it requires
users to manually determine the correct referer string and populate
this setting for the connection -- we cannot do this for them!)
The 'maximum number of features' settings is now always the maximum number of
features requested, even in WFS 2.0 with paging.
For WFS 2.0, we add a checkbox to enable/disable paging and a text entry to
specify the page size (if let to empty, server default is used)
We also add a Detect button so that the WFS version is autodetected.
