Progress<T> fix (added "NewEventHandler")

Avoid using EventHandler<T> explicitly with Progress<T>, I repeat:
Avoid!
Improved Disposing

_handle gets disposed, I assure you.
Readme updates
Naming convention fix
Naming convention fix

I have to continue fixing style in BigInteger
Also there are things to improve here
Added TODO in WorkContext

A dedicated thread may die because of an unhandled exception. I will
probably keep it alive instead of cycling a new one.
Added CencellationToken et al.
Tweak to ThreadingHelper to match Mono's SpinWait
Added SpinWait
Readme updates (again)
Code analysis fix in GCMonitor
Style fixes
Style fix [for (;;) -> while(true)]

Because some tools think that ";;" is weird.
Enforcing naming convention

Renamed private static readonly fields to be "_" followed by lower camel
case.
Global Clean Up

Removing unused using and empty lines.