Reorganised the Group::removeChild and Geode::removeDrawable methods so

that removeChild(Node*), removeChild(uint) and equivilant Geode methods are
now inline methods, not designed to be overriden, and seperated out the
multiple remove method to be called removeChildren(uint, uint) which is
now the only virtual method.  There removeChildren is now the method to
override in subclasses.

This reorganisation requires some call code to be rename removeChild usage
to removeChildren.

src/osg/Geode.cpp

@@ -77,10 +77,10 @@ bool Geode::addDrawable( Drawable *drawable )
 
 bool Geode::removeDrawable( Drawable *drawable )
 {
-    return removeDrawable(getDrawableIndex(drawable));
+    return removeDrawables(getDrawableIndex(drawable),1);
 }
 
-bool Geode::removeDrawable(unsigned int pos,unsigned int numDrawablesToRemove)
+bool Geode::removeDrawables(unsigned int pos,unsigned int numDrawablesToRemove)
 {
     if (pos<_drawables.size() && numDrawablesToRemove>0)
     {