Adding a ValueGenerator to the Redis provider. Moved the common parts of
SqlServerSequenceValueGenerator out into BlockOfSequentialValuesGenerator
and have both SqlServerSquenceValueGenerator and
RedisSequenceValueGenerator inherit from that.
Positive Tests for Negative Cases (adding tests for database error page)
Adding a few end-to-end tests for database error page
Also enabling shared API tests
Making 125 people less mad...

Support store-generated default values

This change allows a property to be marked as using store-generated default values. If no value has been set for the property when the update pipeline inserts the entity the update pipeline will read the value generated from the store. If a value is specified explicitly it will be inserted. This is essentially the same behavior has used for generating keys except that it doesn't involve value generation on Add.

Note that the generation of default constraints in the database by Migrations is not yet implemented so these will need to be setup manually for now.

Also not supported yet is the ability to use this in updates where the semantics are a bit more nuanced.