Add exception handler for REST api
Add exception handler for REST api

Current REST api returns one line message if occurs the
error. However, helper functions raises the exception, then REST api
returns html page instead.

So this adds exception handler to return consistent error handling.

First attempt was @blueprint.add_errorhandler to catch exception, but
we have to exclude "/lodgeit/" from it, and failed.  So, instead,
this adds @rest_errorhandler decorator for each REST methods.

bepasty/bepasty-server,bepasty/bepasty-server,bepasty/bepasty-server,bepasty/bepasty-server