[Alert_collaboration] New design and simulation

[Whitney R. Armstrong]

Hello Everyone,

I have been working on the ALERT design using the preliminary design of 
the front and back drift chamber end plates. I have added a frame to 
form an "ALERT module". On the wiki page you will find some images of 
this full configuration. 
https://clasweb.jlab.org/wiki/index.php/ALERT_Detector_Design

The cad designs are now included in clasdigi as mesh files, and can be 
used in c12sim (not yet in the master branch). Currently all modules 
including the end plates, frame, and scintillator readout boards are one 
mesh solid.  This makes initial simulations easier and can easily be 
broken down into smaller components.

The latest cad files will be linked on the wiki.  Let me know if you 
have any questions. 

Cheers,
Whit