Editor: Support transparent backgrounds on ui elements by removing fixed color assignments
Expand viewport to window size
Editor: Refactor fixed border colors to css classes
Editor: Refactor fixed user-select rules to css
Editor: Extracting FancySelect styles to template
Editor: Update Element.addClass implementation
Editor: Extract embedded style tag to linked stylesheet
Editor: Extracting input styles to template
Editor: Revised dark theme
Editor: Added theme switcher, restored default theme colors plus misc cleanup
Editor: Restored viewport dimension and moved more properties to the stylesheet.