Lift font SCSS partials to theme root

This means that themes which include `light/css/_base.scss` (currently Dark and
Status) won't be forced to have Light's font-faces included.  This only really
matters for Status, which uses different fonts throughout.

res/themes/dark/css/dark.scss

@@ -1,4 +1,4 @@
+@import "../../light/css/_fonts.scss";
 @import "../../light/css/_base.scss";
 @import "_dark.scss";
 @import "../../../../res/css/_components.scss";
-

res/themes/dharma/css/_dharma.scss

@@ -1,5 +1,3 @@
-@import "_fonts.scss";
-
 // XXX: check this?
 /* Nunito lacks combining diacritics, so these will fall through
    to the next font.  Helevetica's diacritics however do not combine

res/themes/dharma/css/dharma.scss

@@ -1,3 +1,3 @@
+@import "_fonts.scss";
 @import "_dharma.scss";
 @import "../../../../res/css/_components.scss";
-

res/themes/light/css/_base.scss

@@ -1,5 +1,3 @@
-@import "_fonts.scss";
-
 /* Open Sans lacks combining diacritics, so these will fall through
    to the next font.  Helevetica's diacritics however do not combine
    nicely with Open Sans (on OSX, at least) and result in a huge

res/themes/light/css/light.scss

@@ -1,3 +1,3 @@
+@import "_fonts.scss";
 @import "_base.scss";
 @import "../../../../res/css/_components.scss";
-