Tuner Base for ElViolin v2

Changes from original:

• deeper electronics cavity (added 5mm to overall cavity depth)
• reworked lower part of body to integrate the deeper cavity
• reoriented the secondary mounting holes for the tuning pegs, mine were horizontally inline, as opposed to angled as in the original version
• added supports of my own design for the shoulder rest mounting undercut and electronics cavity, to allow printing without supports