BackendManager: Cache backend environments to avoid unnecessary requests
Rename internal helper functions to match server terminology.
Fix camel case in EnginioClient: setserviceUrl -> setServiceUrl
Add backend manager function to query backend environments
and combine it with the local environments cache.
Add backend manager function to get backend API keys
e.g. {"backendId" : "ID", "backendSecret" : "SECRET"}
Make the search test use it's own backend.
This is the first step of a migration to per-testcase backends.
Merge pull request #126 from bbandix/backendManager

Backend manager improvements