Make index names unique

[alcohol]

If the names are not unique, SQLITE will throw a fit and refuse to create the schema, e.g.:

$ app/console doctrine:schema:create
ATTENTION: This operation should not be executed in a production environment.

Creating database schema...

  [Doctrine\ORM\Tools\ToolsException]
  Schema-Tool failed with Error 'An exception occurred while executing 'CREATE INDEX package_name_idx ON link_require (version_id, packageName)':
  SQLSTATE[HY000]: General error: 1 index package_name_idx already exists' while executing DDL: CREATE INDEX package_name_idx ON link_require (version_id, packageName)

  [Doctrine\DBAL\Exception\TableExistsException]
  An exception occurred while executing 'CREATE INDEX package_name_idx ON link_require (version_id, packageName)':
  SQLSTATE[HY000]: General error: 1 index package_name_idx already exists

  [Doctrine\DBAL\Driver\PDOException]
  SQLSTATE[HY000]: General error: 1 index package_name_idx already exists

  [PDOException]
  SQLSTATE[HY000]: General error: 1 index package_name_idx already exists

Making them unique solves this.