Update canvas.class.js

Added lockScaleFlip variable to scale object method
Update object.class.js

added lockScalingFlip, if set to true you cannot flip by accident an objec while scaling it.
Update object.class.js

Just grammar
Update canvas.class.js
Update object.class.js
Merge pull request #1584 from asturur/Lock-Scale-Flipping

Lock scale flipping