Refactor network client

This patch implements the following steps in network client refactoring
1) Automatically 'generated' list_, show_, delete_ methods for most of
the resources
2) XML and JSon client implementations inherit common base
3) Every list method now supports filters

This change allow to remove existing list_, show_ and delete_ methods for
simple resources from both clients.

Some tests were fixed to simplify mapping between client method name and
resulting URI (example: list_floatingips instead of list_floating_ips)

Change-Id: I0eb46f8e3d90809dbfc54d4a250cd6aecfdc2c3b
Merge "Refactor network client"