Move to better monotonous increasing timesource about idgen

[RobThree]

27484e7 is a better implementation for the DefaultTimeSource. This implementation should guarantee a forward-only monotonic increasing clock, except between reboots where the time may be adjusted backwards without IdGen noticing.

The most important issue of #1 is thus solved; however: I would still like to move away from the "milliseconds" and go for a more abstract 'ticks' kind of concept. That way we can have the user provide an ITimeSource that, for instance, ticks every second or day or... whatever the desired resolution is. This way the user is better able to control the timestamp part of the generated ID's.

So "part two" of this issue still remains: move away from DateTime and move to "ticks".

[RobThree]

Changed my mind (10bf70f) and went for QueryPerformance counter. Even though it can "leap" a bit sometimes, it is still a strictly increasing (or non-decreasing) timer. You can still run in trouble when you restart your application or system while adjusting the clock in-between but other than that you should be fine. Still: part two remains; I want to move away from "milliseconds" and to "ticks" (be it a second or a millisecond or a century; a tick is what the user defines it to be).

[RobThree]

I just committed 7fc9120; this is a breaking change but does move away from the fixed millisecond resolution. Some more testing & verification will need to be done before calling this RC final.

Feedback is very welcome!

[RobThree]

Released 2.0 today