Remove direct echo db access from mobilefrontend

This revives https://gerrit.wikimedia.org/r/#/c/155663/,
it's reverted earlier because Echo was not being stable,
it's safe now as the Echo code has been deployed to both
deployment branches

Change-Id: I036606a0a706ea898838a36ef92c1a1e658c0a9a
Merge "Remove direct echo db access from mobilefrontend"