Using arc angles to plot an arc is really error prone due to different
options between plotters, and angles defined in Kicad, using this version of
arc plotting from Kicad is no longer allowed in Kicad code.
Also moves most navigation code to SCH_NAVIGATION_TOOL.
Also changes page number href to anchor syntax ('#foo').
Also adds hypertext processing to SCH_TEXTBOXes.
Also adds combobox with schematic pages to text properties dialog.
The problem is that "real" page numbers can be duplicated, so we work around it
by using virtual page numbers instead which are guaranteed unique.
Example "goto:3" will go to page 3. If customised page numbers are used such as
a, b, c, then to go to page b, we should specify goto:2 (i.e. the virtual page
number).
Only SVG can actually handle transparency, but we should at least mimic
the color value of other transparent fills by blending with a (presumed)
white paper.
Fixes https://gitlab.com/kicad/code/kicad/issues/11304
Also fixes some plot bugs with arcs.
Also moves polygonization of arcs (when required) in plotting code
from 5 degrees to calculated based on ARC_HIGH_DEF.
Fixes https://gitlab.com/kicad/code/kicad/issues/5017
Use 4 digits in mantissa as default and when exporting SVG.
Allow 0 as line width: this is the right value to draw filled shapes with no outline thickness.