* ui: Add a way to reliably figure out where the UI is running
The main javascript that we use is at </where/the/ui/is>/ui/assets/consul-ui.js
This uses this fact to provide and base path 'environment' variable to
be used within the app. This is also overwritable via various methods
(testing/development) if we ever need to do that.
* Remove BASE_API_URL, the logic here isn't exactly correct
Right now the API always _has_ to be at http://domain/v1/ i.e. the root
of your domain /v1. If the URL of the ui is set differently to
http://root.com/somewhere/else/ui/ then the API is still at http://root.com/v1
There is definitely a plan to add this env var back in at some stage so
we can potentially allow this to be configured in other ways, but there
isn't a need to do it just yet so we don't need to worry about _how_ to do
this right now.