narrow tool holder

This is a narrow version of a tool holder inspired by the thing mentioned above in the ancestry. I liked that thing with the caveat that when I have the gen4 interface hooked onto the front of my ToM, there wasn't enough room to hang my tools too. So, I took inspiration from the original thing, redrew it and made two design changes:

1. rotate on Z axis 90 degrees to make a narrow surface.
2. added a second level so that my tools would have more support and be less likely to fall out. The L-bend of my hex keys just loved to slip through the single holes. Not anymore.