Simplify parameters on sl-able and sl-unable

[jonathandavidson]

There is some unnecessary complexity in the provider parameter when an object is supplied. In order to simplify this feature without sacrificing any functionality, the sl-able and sl-unable components will be revised as follows:

• The behavior parameter will be renamed resource and will otherwise remain unchanged
• The provider parameter will be renamed activity and will no longer accept an object, only a string corresponding to the Behavior Group key name used in the Behaviors structure
• An additional possible parameter will be added which accepts a boolean, computed property that evaluates to a boolean, or a function returning a boolean. This will take the place of the behaviors object passed in through the provider parameter since only one behavior (activity) is being evaluated in a component instance.
• The possible parameter will be observed to make the component responsive to changes in the value supplied.

[notmessenger]

@jonathandavidson For clarification, the possible parameter in the 3rd bullet point in the previous comment will accept any input that resolves to a boolean, be it an actual boolean, a computed property or a plain function, correct?

[jonathandavidson]

@notmessenger Correct. I have updated the description to reflect that clarification.