Re-introduce ORM samples with dummy database plugin

[djones6]

#109 removed the ORM examples from Kitura-Sample as it otherwise requires users to install Postgres dependencies.

However, Kitura-Sample could include ORM and Kuery samples that work out-of-the-box, by using a 'dummy' database plugin (something that is backed by a simple in-memory structure for example).

I believe such a thing is already implemented in the Kuery tests. Could we use this as the basis of something simple that would provide enough functionality for the purposes of the sample?

[Andrew-Lees11]

Closing now the pr which adds this functionality has been merged.