make custom data entities (data_entity.module) cacheable using entitycache

The data_entity.module is a great module to define custom entities quickly.
It would be really helpful to also make them cache-able using entitycache.module.

The instructions from the description

- Create a cache_entity_$myentity table/bin.
- Specify EntityCacheDefaultEntityController as your controller class in hook_entity_info(), or extend it.
- Never update your entity tables outside of save/delete API calls.