Make editor color customizable by theme.

[dram]

This PR make editor usable in dark theme. Here's a screenshot.

This screenshot is run with this PR, PR #73 and following configurations:

preferences outliner theme: preferences outliner themes night.

preferences desktop backgroundColor: preferences outliner theme bodyColor.

selfCatOrObjModel moduleSummaryFontSpec size: 16.
selfGeneralSlotModel undeclaredTitleFontSpec size: 14.
selfGeneralSlotModel privateTitleFontSpec size: 14.
selfGeneralSlotModel publicTitleFontSpec size: 14.
generalCategoryModel objectTitleFontSpec size: 16.
generalCategoryModel objectTitleFontSpec style: 'bold'.
generalCategoryModel subcategoryTitleFontSpec size: 14.
ui2_textField fontSpec: globals fontSpec copyName: '9x15bold' Size: 15.
ui2Menu defaultFontSpec: ui2Menu defaultFontSpec copySize: 16.