Document the way to use provides/requires and the effects on task result finding

Document the way to use provides/requires and the effects on task result finding, currently there are 3 ways to interpret a tasks provides that affect exactly what the task can return (and how what the task returns are mapped and picked up for usage by other tasks). We should likely add some documentation that clearly explains this (so the user of taskflow doesn't have to go finding how this works in the code) so that its very obvious which ways can be used (and how).