Using integer types for animation duration

[sherief]

The ozz animation format uses a float for duration, in contrast to the more deterministic long long used by FbxTime. Would you consider updating the format to use int64_t for duration, with the classes providing the same API that converts to floating-point seconds at runtime? The file format being deterministic across multiple machines has some value in build pipeline automation, and I just got bitten by this myself. Would be happy to contribute to the implementation if you think it's something you'd consider merging, just don't wanna work on something that conflicts with your goals for the project.