Layer Bitmap: migration of parameters to ValueBase type. Needed modification of code from Layer Composite
Add missing set_static_defaults for Circle layer
When set or get a parameter, preserve the static/interpolation form parameter when get and assume the static/interpolation from value when set.
Remove traces of set_param_static and set_param_interpolation. They are not needed.
Layer Composite: migration of parameters to ValueBase type. ParamDesc now there is only one constructor that gets a ValueBase as first parameter.