b3CreateBoxCommandSetColorRGBA: allow to specify color when creating bodies through shared memory API

Parse and use colors from URDF file (single rgba color per link, not per visual)
Rename btMultiBody 'stepVelocities' to 'computeAccelerationsArticulatedBodyAlgorithmMultiDof'
btHashMap, add const Value* operator[]
remove a few more obsolete btMultiBody methods (on the non-multi-dof path)
fix spelling typo in fillConstraintJacobianMultiDof (fil -> fill)
Add mention to Jakub Stepien for his work on btMultiBody

examples/Importers/ImportURDFDemo/URDFImporterInterface.h

@@ -24,6 +24,8 @@ public:
     
     ///pure virtual interfaces, precondition is a valid linkIndex (you can assert/terminate if the linkIndex is out of range)
     virtual std::string getLinkName(int linkIndex) const =0;
+	/// optional method to provide the link color. return true if the color is available and copied into colorRGBA, return false otherwise
+	virtual bool getLinkColor(int linkIndex, btVector4& colorRGBA) const { return false;}
     
     virtual std::string getJointName(int linkIndex) const = 0;