add real-time safe Inverse Dynamics library+test+utils

an example for the example browser will follow.
thanks to Thomas Buschmann

Extras/InverseDynamics/MultiBodyNameMap.hpp

@@ -0,0 +1,54 @@
+#ifndef MULTIBODYNAMEMAP_HPP_
+#define MULTIBODYNAMEMAP_HPP_
+
+#include "BulletInverseDynamics/IDConfig.hpp"
+#include <string>
+#include <map>
+
+namespace btInverseDynamics {
+
+/// \brief The MultiBodyNameMap class
+/// Utility class that stores a maps from body/joint indices to/from body and joint names
+class MultiBodyNameMap {
+public:
+    MultiBodyNameMap();
+    /// add a body to the map
+    /// @param index of the body
+    /// @param name name of the body
+    /// @return 0 on success, -1 on failure
+    int addBody(const int index, const std::string& name);
+    /// add a joint to the map
+    /// @param index of the joint
+    /// @param name name of the joint
+    /// @return 0 on success, -1 on failure
+    int addJoint(const int index, const std::string& name);
+    /// get body name from index
+    /// @param index of the body
+    /// @param body_name name of the body
+    /// @return 0 on success, -1 on failure
+    int getBodyName(const int index, std::string* name) const;
+    /// get joint name from index
+    /// @param index of the joint
+    /// @param joint_name name of the joint
+    /// @return 0 on success, -1 on failure
+    int getJointName(const int index, std::string* name) const;
+    /// get body index from name
+    /// @param index of the body
+    /// @param name name of the body
+    /// @return 0 on success, -1 on failure
+    int getBodyIndex(const std::string& name, int* index) const;
+    /// get joint index from name
+    /// @param index of the joint
+    /// @param name name of the joint
+    /// @return 0 on success, -1 on failure
+    int getJointIndex(const std::string& name, int* index) const;
+
+private:
+    std::map<int, std::string> m_index_to_joint_name;
+    std::map<int, std::string> m_index_to_body_name;
+
+    std::map<std::string, int> m_joint_name_to_index;
+    std::map<std::string, int> m_body_name_to_index;
+};
+}
+#endif  // MULTIBODYNAMEMAP_HPP_