Don't unwrap Struct items during merge()
Don't unwrap Struct items during merge()

The merge() method wasn't properly wrapping items it added. Since
__init__, update(), and merge() all need to have a similar wrapping loop
they have been merged into an _extend() method that does it all.
kovacsbalu/coil,marineam/coil,marineam/coil,tectronics/coil,tectronics/coil,kovacsbalu/coil