* Remove redis_commands field from redisexperiment model

Wires up the termination framework as a configurable service that allows configuring an arbitrary set of termination criteria,
including custom ones that can be registered by adding them to the terminator.CriteriaFactories map. This allows for
custom pluggable termination criteria that may rely on internal systems (e.g. check for pages using an internal library)
that can hook into the monitoring system provided by the termination framework.

Includes a single termination criteria as an example, which simply terminates experiments after they have run for a configured
amount.

Rejigs the monitoring class a bit to allow for per config type termination criteria

* add primary keys constraints to experiment_run and experiment_config tables

* Enforce cancellation reason
* increase termination reason char count limit to 100
* more api restrictions
* make data required

This reverts commit 517b1aba.