#198 introduced a float-field translucency

... and created a getter and a setter for it.
 #198 properly implemented clone()
 #198 set wmsCapabilities

When the SlidableWMSServiceLayerGroup is created from a JDOM-Element,
the wmsCapabilities is also set for its sublayers.
 #198 comments
Merge branch 'feature/198-sliderableLayer-compatible-with-headlessmapProvider' into dev