Recording StrokeFrame as Differences Instead of States

• Modify the recording of StrokeFrame from a state-based approach to a differential approach.
• The current implementation is not very intelligent.
  • It simply consumes a lot of information.
  • It does not allow for combining Frames together.
• However, we need to think about how to handle past modifications.
  • Simply adding up the differentials could lead to unexpected results.

#implementation#pkineto