SCHEMA CHANGES: Improve MySQL schema: (closes #480)

- explicitly ask for InnoDB
- use BIGINTs as primary keys
- add a BIGINT primary key to staged; chars as primary keys hurt indexing
- INDEX(foo) when foo is already UNIQUE makes a duplicate index
- email.user is now a foreign key to user.id
- add 'NOT NULL' constraints
- for varchar(N) where N < 255 and the strings are fixed length,
  it's slightly more efficient to use char(N)

Signed-off-by: Lloyd Hilaiel <lloyd@hilaiel.com>