Implemented a view and form compatible with rapidsms v0.17.0

The view accepts incoming message from envaya android app and the form
cleans and processes the data.
Implementing a dummy backend class for outgoing message cycle.
Fixed the problem with problems identifying the identity/connection for a msg.
Outgoing messages are now enqueued in the database for delivery.
Outgoing messages are now successfully sent to the EnvayaSMS Android app

This completes the outgoing message cycle.
Fixed a bug with handling of actions and made logging messages better.
Changed installation info in README as per new changes.

The app is now called envayasms and the existing parameters,
URL, password and max_delay are no longer supported.
Added info in README about how the whole app works.