Refactor theme naming to match "official" color names

[lschmelzeisen]

style/themes/base.css

Lines 2 to 3 in 4d0aead

	--theme-fg: var(--lm-regular-fg);
	--theme-bg: var(--lm-regular-bg);

• Should be renamed to --theme-regular-fg/bg

style/themes/base.css

Lines 8 to 10 in 4d0aead

	--theme-special-bg: var(--lm-special-bg-grad-gray);
	--theme-special-skewed-bg: var(--lm-special-bg-grad-gray-skewed);
	--theme-special-stacked-bg: var(--lm-special-stacked-bg-grad-gray);

• Should be renamed to include -grad and the names should follow the same structure as the lm/dm names.

While on this:

• Status colors should be added to themes.

[raphaelmenges]

Status colors should be added to themes.

Status colors are in the theme but the keyword status is left out.