Add import/export/paste model functionality to editModels.js
Add ModelTree::getModelAt
Merge branch 'master' of git://github.com/highfidelity/hifi into 19783

Conflicts:
	interface/src/scripting/WindowScriptingInterface.cpp
	interface/src/scripting/WindowScriptingInterface.h
separate muscle constraints from joint constraints
formatting and minor tweaks to constraint strengths
more perfstats for ragdoll simulation
add Shape::_id
namechange for Shape::_id
fix old copy-n-paste typo
fix old bug: rotation of CapsuleShape not updated

when setting endpoints directly
add PhysicsSimulation::_frame
remove unused Constraint::_type
add CollisionInfo::getShapePairKey()
Add pasteModels
Add LocalModelsOverlay
Add SendModelsOperation
Implement pasteModels in Clipboard
Add localmodels overlay type
Update and add localModels overlay to editModels.js import/export
Update LocalModelOverlay to work prorperly with translations