Add network connection methods

[imurchie]

Two methods needed, one to get the network connection, the other to set it.

The network connection is specified as a bitmask, the details of which are here. Feel free to make whatever structure would be idiomatic for the values.

Getting the connection (e.g., wd):
GET, /wd/hub/session/:sessionId?/network_connection

Setting the connection (e.g., wd):
POST, /wd/hub/session/:sessionId?/network_connection
with payload like "parameters": { "type": 1 }