Automatic task-def creation from task creation request

[dcgoss]

In cognoma/core-service#68, when core-service creates a task with task-service it includes the name of a task-def in the request, such as "classifier-search". Currently, if this task-def does not already exist the request will fail. It would be graceful if task-service can take this task-def name from the task create request and automatically create a task-def before creating the task.