Added the ability to load .env files for preloading database credentials

After some discussion, it's been decided to add partial .env support.

This means if you have a laravel style .env file within the current working directory, you'll get offered the chance to load the database credentials from it - speeding up the repetitive attempts.

The supported options are

DB_CONNECTION=mysql
DB_HOST=localhost
DB_PORT=3306
DB_DATABASE=my_database
DB_USERNAME=root
DB_PASSWORD=password
DB_PREFIX=wp_