Enable generic component locating

We need a consolidated way to orient various components in space relative to each other without having to deal with flipping coordinate signs, etc in code. Locations of components can be specified in the config.

We should use ROS' [transformations](https://pypi.org/project/transformations/) library, which is self-contained, and contains general utilities for rotation, scaling, etc.

Aside, but relevant: ROS supports a way of exporting kinematic trees from Solidworks with a "[URDF file exporter](http://wiki.ros.org/sw_urdf_exporter)". This would be a great way to specify the locations of objects without needing to bookkeep the file manually.