Move to gorm

## Warrning
~~1. Test fails because this is ORM problem ( i think tomorrow this will be fixed ) https://github.com/jinzhu/gorm/issues/202~~
2. This PR change table column names, and some SQL Queries

## Features
1. Support PostgreSQL, SQLite, MySQL
2. Migrations via ORM
3. Test data renamed to fixtures and use ORM too
4. Some SQL Queries now use JOIN
5. SQL log, by default disabled, but enabled in `make run`, or `droned --dbdebug=true`
6. Use DATABASE_URL instead driver/source flags (*tcp* only for PostgreSQL and MySQL)
```sh
DRONE_DRIVER="sqlite3" DRONE_DATASOURCE="/home/bugagazavr/drone.sqlite" make run
DRONE_DRIVER="postgres" DRONE_DATASOURCE="user=postgres host=127.0.0.1 port=5432 dbname=drone sslmode=disable" make run
DRONE_DRIVER="mysql" DRONE_DATASOURCE="root@tcp(127.0.0.1:3306)/drone" make run
```