Option to extract meta-data under keyframe based format

[bchevalier]

Right now the JSON metadata file contains the transformation matrices for every frame of every symbol within a movie clip.

The idea is to convert the list of transformation matrices for every frame of a given symbol into a list of keyframes with corresponding easings. It can be done in 2 steps:

• 1. Do some math to determine the position, rotation, skew and origin of a symbol from a transformation matrix.
• 2. Determine easings that can be used to generated keyframes using in priority the flash easing method:
     t = t + t * ease - t * t * ease .