use outline icons instead of solid icons in palette and context pad

[hofstef]

The modeler uses the outline version of Google's Material icons,. However, in the context pad and in the palette, solid icons are used instead.
The icons should be unified. Outline is the style of choice because it is more printer friendly.

[hofstef]

The icons for the palette and the context pad are defined in a font file that only contains solid icons. Google has not updated the font in years.
Alternatives:

• an alternative icon set that comes with a font (fontawesome?)
• make our own font with the icons that we need
• use svg instead of fonts; however, this breakes highlighting in the context pad.

[AlexanderZellober]

Found a way to use svg that does not break highlighting in the contextPad.