Add data-driven styling to editor

Builds off of the ZoomSpecField component with separate options for
handling data-driven properties. Reuses most of the zoom field
functionality with tweaks that I tried to keep as small as possible, and
the layout is based off of comments on the existing issue.

src/styles/_components.scss

@@ -104,13 +104,13 @@
 .maputnik-action-block {
   .maputnik-input-block-label {
     display: inline-block;
-    width: 43%;
+    width: 35%;
   }
 
   .maputnik-input-block-action {
     vertical-align: top;
     display: inline-block;
-    width: 7%;
+    width: 15%;
   }
 }