Add Priority setting for Tasks

#### Feature Request Description
There are times when we submit a large set of tasks that have no dependency on each other, and it would be preferred if a subset of those tasks executed first. We cannot set dependencies on these tasks as that would cause issues with our workflow. Thus, the ability to give a subset of these tasks a slightly higher priority than the rest would be the ideal solution.

#### Describe Preferred Solution
The preferred solution would be to add a "Priority" property on the Task, as it currently exists on the Job. When the scheduler determines which task should be assigned to a node, the Job priority would still be checked first. After that, task priority would offer a second level of prioritization.