Added URDF and moveit package for ABB IRB6640 robot

After review of the previous pull request by my colleague Simon, we decided to change our IRB 6640 packages to adhere to the naming convention used in the other ABB packages. Since that meant renaming most of the files and making a lot of small changes, we decided to make a new pull request.

Note that this is the IRB6640 185/2.8 version.
Note that the meshes of the visual model are quite large (>10MB)