Initial DB rewrite work

- Switched from activerecord gem to sinatra-activerecord
- Database configuration now lives in config/database.yml
- Rakefile to enable running of database tasks
- First stab at new database structure, written as ActiveRecord
migrations
Model changes to reflect new database structure
Corrected meter relationship
Added example database config file
Hotfix - change name of database.yml.example to database.yml
Pushed database.yml (was accidently ignored)
Added import log table to model
Merge pull request #7 from EDEN-Energy/db_rewrite

New DB Structure