* Add a way to set the local datacenter
* Amend step so we can positively and negatively look for elements
* Add a data-test selector so we can get to the topology series graph
* Add a couple of tests to verify the series graph shows/doesn't show
* ui: Keep track of existing intentions and use those to save changes
Previously we risked overwriting existing data in an intention if we
tried to save an intention without having loaded it first, for example
Description and Metadata would have been overwritten.
This change loads in all the intentions for an origin service so we can
pick off the one we need to save and change to ensure that we don't
overwrite any existing data.
John Cowen