Mechanism initial and idle requests

[rcahoon]

Description

Add customization points for a Mechanism to specify an Initial request and Idle request.

The Initial request will be set as the request when the Mechanism is first created. If the Mechanism also defines an Idle request, then the Initial request will only be passed to the first call to run() (after that, the Idle request may take over). Otherwise, the Initial request will be passed to run() until something calls setRequest() on the Mechanism.

The Idle request will be set as the request for the Mechanism when no Procedures are reserving the Mechanism.

Each Mechanism is required to have an Initial request; specifying an Idle request is optional. If no Idle request is specified, the Mechanism will continue to run its last request after the reservation ends.

How Has This Been Tested?

• Unit tests: Unit tests for new functionality are included
• Simulator testing: [Add your description here]
• On-robot bench testing: [Add your description here]
• On-robot field testing: [Add your description here]