Add a nodepool command

Moves the daemon command to nodepoold.

Refactor config handling a bit in NodePool to make the config
objects just contain information by default (though things
such as database handles and managers may get added to them
later as needed).

Start with the list and image-list commands.

Change-Id: If2ba7bca7ab4ef922787176af87ad5de31ae4b3e

requirements.txt

@@ -13,3 +13,4 @@ sqlalchemy>=0.8.2,<0.9.0
 pyzmq>=13.1.0,<14.0.0
 python-novaclient
 MySQL-python
+PrettyTable>=0.6,<0.8