Mistral PoC

We need to create a small PoC project illustrating main Mistral ideas. It should include the following capabilities:

- Basic Workflow Engine capable of analyzing task graphs, resolving dependencies between tasks and processing them in the right order
- Simple storage (RDBMS for now) and access layer to it for storing task graphs and workflow execution states
- Basic DSL for defining tasks, task dependencies, actions and action transports (currently HTTP and AMQP)
- REST API for uploading task graphs and executing workflows
- Demo app (a client for Mistral that schedules workflows and handles actions)
- Necessary test suite to validate the above functionality