Slam steps refactoring

Refactor SLAM main steps for better clarity.

• Add CheckFrame step that runs all sanity checks of incoming frames
• Perform motion extrapolation in EgoMotion step as it aims at estimating relative motion
• Rename UpdateFrameAndState to UpdateFrameTime and modify point-wise time field only if undistortion is enabled
• Minor changes of printed info and reorganization of other steps

@julia.sanchez @nick.laurenson PTAL