New function - load external WMS, WFS, GML, SHP

[JakubPelka]

Idea / Need: Create a button that will make it possible to load into the browser external data like WMS, WFS, GML, SHP, DXF etc. If user has access to data sources that are no accessible via map right now - it is good to make it possible for the client to load that data. Data can not be stored and must be presented only in the viewer (for ex. SHP, DXF).

+WMS/WFS button should open a window where one can paste link and chose layers to present in the viewer: Similar functionality is quite popular in many map services. Just one of the examples.