Log Message:
(cad/solvespace) Updated 3.0 to 3.1

(You may see RC1, bellow, but code is Release 3.1)
Changelog
=========

3.1  - Release Candidate 1
---

Constraints:

* Arcs length ratio and difference.
* Arc & Line length ratio and difference.
* Allow comments to be associated with point entities.

Sketching:

* Support for pan, zoom and rotate trackpad gestures on macOS
* Add "exploded view" to sketches via "\\" key. Shows sketch \ 
elements separated
  by a configurable distance perpendicular to the sketch plane.
* Added Feet-Inches as a unit of measure. Inputs are still in inches.
  But the display shows feet, inches, and fraction of an inch.
* Added an optional "pitch" parameter to helix extrusions (in the text \ 
window)
* Allow use of Point & Normal to define "sketch-in-new-workplane".
* Update "Property Browser" live while dragging the sketch.

MISC:

* Add a link to the GitHub commit from which SolveSpace was built in the Help
  menu.
* Make all points, vectors and normals shown in the Property Browser into
  active links. This makes them explorable and selectable.
* Load 16bit PNG images correctly by re-scaling to 8bit.
* Fixed hang when trying to display characters missing from the embedded font.
* The main window vertical size can be as small as the toolbar.
* Configurable "SafeHeight" parameter instead of the fixed 5mm for \ 
G-code export.
* Add Spanish / Argentina translation.
* Move "perspective factor", "lighting direction" and \ 
"explode distance" from
  the "configuration" screen to the "view" screen.
* Add a "∆" suffix to groups which have "force to triangle \ 
mesh" ticked
* Gray the group name in the text window for groups with suppressed solid model.
* Added the ability to Link STL files.
* When linking circuit boards (IDF .emn files) show keepout regions as \ 
construction entities.

Performance:

* Speed up sketches with many constraints by roughly 8x by using the Eigen
  library in the solver. The maximum unknowns increased from 1024 to 2048.
* Add a "suppress dof calculation" setting to groups - increases \ 
performance for
  complex sketches.
* More changes to the ID list implementation.