Adding GET REST interface

Adding a minimun GET REST interface that allows both to get geolocation data
and status for both electric panels and phase lines, we are using django rest
framework to simplify things and to be able to generate the API page easily
Improving models

Several improvements
* Adding get_absolute_urls
* Calculating phase line status based on last event for each line
Updating views
Adding more resolve functions to models
Fixing typos
Dropping methods
Import models and use that instead of just the types
There's no need to expose power lines to context, exposing text constants to context
Reorganize urls
Updating views, adding code for dynamically changing color of powerlines based on status