data: Update stylesheet with upstream design

- adjust main font size
- adjust margins and border radii
- drop borders from keys
- put more items in common.css
- update dark and light style definitions
- use mixing of fg color wherever possible

data/common.css

@@ -1,6 +1,33 @@
-/* Theme independent style */
+/* Theme independent styles */
+
+sq_view {
+    font-family: cantarell, sans-serif;
+    font-size: 1.5em;
+}
+
+sq_button {
+    border-radius: 4px;
+    margin: 2px;
+}
+
+sq_view.wide sq_button {
+    margin: 3px;
+}
+
+sq_button.latched,
+sq_button.locked {
+    font-weight: bold;
+}
+
+sq_button.action {
+    font-size: 0.75em;
+}
+
+sq_button.small {
+    font-size: 0.5em;
+}
 
 sq_view.pin sq_button {
     border-radius: 0px;
     margin: 1px 1px 1px 1px;
-}
+}