Add create network 'post_org_vdc_network' request
Add get_org_vdc_networks & delete_network request handlers

* No Mocks or tests as yet
Flesh out Mock data with multiple vDCs & networks

* we need this so we can test behaviour of shared org vdc networks
* static uuids for networks, so we can play with deleting in Mock
add basic Mock support for get_org_vdc_networks
add Mock mode for delete_network
add tests for delete_network, get_org_vdc_networks
add Mock for post_org_vdc_network, plus basic test
correct name of post_create_org_vdc_network
more tidy of post_create_org_vdc_network as per nick discussion
reorder network tests so failing tests fail first
redo options for post_create_org_vdc_network to match XML
Remove get_org_vdc_network - crap code, not needed
shift XML logic into OrgVdcNetwork generator
correct capitalisation with IsShared in Mock