Add support for multiple instances to access data from same datastore

What's Changed

• Fix race in same table being updated by datastore/protostore tests by @krishnamiriyala in #17
• Do not require context when registering structs by @jeyhun in #19
• Fix race in multiple create triggers being called by @krishnamiriyala in #21
• Cache and avoid repeated calls to schemaParse by @krishnamiriyala in #22
• Add instancer interface with With/GetInstanceId methods by @krishnamiriyala in #23
• Add support for multi instances access data from same datastore. Closes #18 by @krishnamiriyala in #20

Full Changelog: v0.0.4...v0.0.5