Added file backend
Removed redis backend

The overall goal is to make lovebeat as standalone as possible
to provide easy deployment. Adding a requirement to redis is not
in line with this goal, so we deprecate it.
dashboard: Auto-updating service list every minute
Refactoring service layer
Muted log printouts when creating service/view
Added HTTP API for setting/getting alert mail recipients

The functionality to send the mails are not yet in place, though.
dashboard: Added UI for setting alert mail recipients
Refactoring: View commands go into separate channels
Refreshing views is done directly, not via channel

This is to avoid a future potential deadlock, and also because
it's not really necessary now when everything is in memory.
Refactoring: service commands go into separate channels