Vertex precision

[Philippe Hurbain]

Since no feedback was given, here's what's been implemented:

A warning is displayed if a file of type Part, Shortcut, or Subpart has >4 decimal precision.
A warning is generated if a file of type Primitive, 8_Primitive, or 48_Primitive has >5 decimal precision.

My expectation is that author justify this warning if a file contains no curved geometry. Part reviewers are to use their discretion for all other cases.

While 4dp is fine for position values (3 is probably enough in most cases, except for fine 3D patterns) I'm afraid that the 4dp threshold is too low for rotation matrix coefficients, needs 5dp to get good enough results.