Complete the CommerceStoreType / CommerceStore entity type definitions

The CommerceStoreType / CommerceStore entity types have been implemented as reference entity implementations. They are incomplete but currently provide the following functionality:

• Defines the CommerceStoreType configuration entity type to serve as bundle definitions for CommerceStore entities.
• Provides a UI for creating, updating, and deleting CommerceStoreType entities.
• Supports managing fields / forms on CommerceStoreType entities via the "admin-link"
• Defines the CommerceStore content entity type with a few default properties (store name, store e-mail, and default currency).
• Provides a UI for creating, updating, and deleting CommerceStore entities.

The big idea here is that at least one store entity representing the online store's "global settings" within Drupal must always be defined. A website may define more than one store as need be to accommodate multiple domains, multiple sellers, fulfillment centers, etc. This means we need additional functionality out of the entity type, including:

1. Forcing the creation and management of at least one store entity.
2. Determining if any other fields will be necessary.
3. Figuring out what the display URL / requirements are of store entities.

Additionally, in order to make these entity types serve as the reference points for other entity types, we need to make a few improvements to the module:

1. Add a description property to the CommerceStoreType entity type.
2. Update the module to support redirect routes instead of directly setting $form_state['redirect'].
3. Replace the store entity list at admin/commerce/config/store with a default View.
4. Add finer-grained access control (i.e. supporting more than just a single administrative permission; the typical bundle level CRUD permissions pertaining to any / own entities).

We aren't currently planning on revision support for store entities, so another entity type (CommerceOrder?) will have to be the reference implementation for that.

If anyone wants to tackle one of the items in this issue, just create a new issue for the work and link it in here.