Window: rewrite Navigation section, added History

[Maciej Stachowiak]

Hi everyone,

I rewrote the Navigation section of Window Object 1.0 to be painfully  
exacting about the conformance requirements, including detailed  
algorithms for performing navigations, etc. I believe most of this is  
technically accurate given my testing, but most of it is open to  
revision based on results from the test suite.

I also added in History since there was consensus that it should be  
added, in fact I put it in the same section since it had to rely on  
many of the same definitions and algorithms.

The main problem with the new text is that it is really really dry.  
Lots of lists of steps and function-like syntax, not much friendly  
prose. But I think navigation actually is quite complicated, and it  
takes a fair amount of detail to specify it in a truly interoperable  
way.

Anyway, comments welcome even though there are still a handful of  
pieces missing. Let me know especially if the text is hard to  
understand or appears to overconstrain implementations.

Regards,
Maciej