Install a python script executor into the template

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
template list

Puts a cache on the pool object of the templates for speed
Change the way the ip address is determined from the init script

Don't use xapi, get the address from the management interface
directly.
Refactor xs_ops a little
Tidy up xs_ops, add make pool function.
Merge pull request #4 from jonludlam/new-stuff

New stuff