small optimize
rename RigEngine to JXAnimationEngine

implement JXAnimation
rework animation state
some basic idea on jxAnimatonCombo
ofxShaderProgram now very flexible
more implement on jxAnimation
add some genius code

not sure if it works or not, but i'm gonna do it by this way. thanks to
redbull and chocopie to make this possible.
improve code readability

replace hard coded number by named constants
shorten code for animation loading
fix small mistake