Grooved bearing lever for the Titan extruders

A grooved lever design in progress for the titan extruder. The base design of the lever based on [this](https://grabcad.com/library/e3d-titan-extruder-2) model. I changed it to be easier to print FDM and added space for a 12mm wire bearing (grooved bearing).

The motivation for the grooved bearing is to fix the issue of the flat stock bearing flattens the filament hard enough to make it jam. [Here's another similar model](https://www.thingiverse.com/thing:2185353) on Thingiverse in case you do