Checks WMS/WFS for each fields in the CFG when saving

[Gustry]

When saving the CFG, we need to check for each tool if the field is published for WFS :

• Locate by layer:

  • display field - WFS needed
  • optional groupby - WFS needed
  • display the geometry : qgis server needed

• Attribute table:

  • primary key : WFS needed
  • fields to hide, no need to check for WFS

• Layer editing :

  • snap layers must be WFS enabled (done in 0450421)

• Tooltip layers:

  • list of fields separated by comma WFS needed
  • display geom : needs qgis server checkbox

• Dataviz :

  • X field : WFS needed
  • Y field in each trace : WFS needed
  • Z field
  • Color field

• time manger

  • start field : WFS enabled
  • end field : WFS enabled

• Atlas :

  • primary key : WFS enabled
  • feature label : WFS enabled
  • sort field : WFS enabled
  • highlight geom : qgis server checkbox

Not concerned :

• Filter by attribute
• Filter by polygon
• Attribute table → Hidden fields...
• Form filter

CC @mdouchin @rldhont if I made any mistake