[Web Timing] Interface names

Since user agents expose the interface names to the DOM, I'd like to
reconsider the interface names as a whole to get a consistent scheme.

Spec              IE                                WebKit
Performance       MSPerformancePrototype            Performance
NavigationInfo    MSPerformanceNavigationPrototype  Navigation
NavigationTiming  MSPerformanceTimingPrototype      Timing

I recommend we standardize on Performance, PerformanceNavigation, and
PerformanceTiming.

For every other interface I checked, IE uses a Prototype suffix, but other
UAs don't use it and it isn't in any specs that I've found. So I assume that
we should standardize on something without Prototype and IE will might add a
Prototype suffix for internal consistency.

Thoughts?

-Tony