Make better database schema.

Remove unused tables.

Create indexes.

Insert dummy data for testing.
Change user id to primary key instead of email.
Add method Donation.isVerified.
Fix Project creation.

Change Project model:

    Replace $duration with $expiration_time.
    Add fields: $needs_volunteers, $youtube_id.
    Add relations: donations, money_promised.
    Add some rules.

Tidy up Project controller, views, and forms.