Theme material-dense

[texodus]

Adds a dense Material theme variant. Also changes:

• Fixed side-effect order in toggleConfig() method to correctly set state when button is quicklly pressed (regression).
• Fixed perspective-viewer-hypergrid issue which caused console error (from Add selectable attribute to perspective-viewer #842).
• Adds --hypergrid-row--height style property.
• Adds throttle attribute, which overrides perspective-viewer's default adaptive framerate.
• Reworked perspective-phosphor maximize functionality from toolbar to context menu using Phosphor's. "single-document" mode.
• Fixed a yarn version incompatibility (from Python build overhaul #839)
• Fixed a phosphor error message due to over-aggressive default faux-hypergrid event binding.
• Made CMake's log output a little less brutal.

Old:

New:

[texodus]

Reviewed offline with @zemeolotu