Fixes issue #19 - implement "proportional leniency" and "lonely tasks"

[Malkiz]

Fixes issue #19.
This PR implements the missing "proportional leniency" and "lonely tasks" as defined in the spec.

Also -
I included some fixes that haven't been merged yet from other PR's, better cleanup (to allow GC) and more configuration control.

I don't have the time or energy to comply with all the "contribution guidelines" or split this into multiple PR's.
Use it however you want, or don't, I don't mind either way.

Thanks.

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