Add a mode layer that switches preconfigured layers according to a (e.g. application) mode

[helllth]

With this layer it should be possible to assign certain layers to different modes. After initializing the layer with that information the layer can easily be switched by switching the mode.

With this kind of a layer one can avoid the adding and removing of the same layers over and over again.

Think of it as a toggle button group of layers ;-)

The layer is needed in this contract: cismet/wupp#96

[helllth]

Example Configuration:

<Layers>
    <ModeLayer>
        <Mode key="A">
            <WMSServiceLayer name="Stadtplanreihe farbig" title="" visible="true" enabled="true" translucency="1.0" bgColor="0xF0F0F0" imageFormat="image/png" exceptionFormat="application/vnd.ogc.se_xml">
                <capabilities type="OGC" active="false"><![CDATA[http://geoportal.wuppertal.de:8083/deegree/wms?VERSION=1.1.1&SERVICE=WMS&REQUEST=GetCapabilities&]]></capabilities>
                <wmsLayer name="R102:stadtplan2007" title="Stadtplanreihe farbig" enabled="true" style="default" info="false" />
            </WMSServiceLayer>
        </Mode>
        <Mode key="B">
            <WMSServiceLayer name="WebAtlasDE" title="" visible="true" enabled="true" translucency="1.0" bgColor="0xF0F0F0" imageFormat="image/png" exceptionFormat="application/vnd.ogc.se_xml">
                <capabilities type="OGC" active="false"><![CDATA[https://sg.geodatenzentrum.de/wms_webatlasde__60d825c3-a2c2-2133-79c0-48721caab5c3?SERVICE=WMS&REQUEST=GetCapabilities&VERSION=1.3.0]]></capabilities>
                <wmsLayer name="1" title="WebAtlasDE" enabled="true" style="default" info="false" />
            </WMSServiceLayer>

        </Mode>
    </ModeLayer>
</Layers>

The Mode can then be set with e.g.:

layer.setMode("A");