Merge lp://staging/~julian-edwards/gwacl/network-configuration into lp://staging/gwacl

Add the SetNetworkConfiguration request xml

Add the SetNetworkConfiguration request xml.

I learned several things while getting bogged down for hours in this branch:

1. You can't put ",attr" in an xml chain like this `xml:"node>subnode,attr"` it just gets silently ignored and becomes an attr of the containing struct's node name.
2. Go will panic in its marshaller if you try and define multiple attrs on a node using an array
3. Because of (1) you need to write stupidly complex deep structs if a low-level node needs an attr
4. I need more coffee to deal with this crap
5. xml parsing in Go is utterly hideous
6. The Equals checker could do with diff output for large strings; it feels like going back to huge failing doctests
7. Kill me now.