Overhaul form control and button sizing, and some type styles

* New padding approach with separate horizontal and vertical padding
variables
* Improved sizing in large and small buttons and form controls
* Dropped the `.btn-mini` (since we have no `.input-mini` to match, and
holy fuck those were small buttons)
* Dropped the `.pagination-mini` as well because once again, to hell
with such small components
* Changed `@line-height-headings` to `@headings-line-height`
* Removed the `@headings-font-family` because it was honestly kind of
useless

docs/assets/css/docs.css

@@ -294,6 +294,11 @@ body {
   margin: 0;
 }
 
+/* Forms */
+.bs-example-control-sizing input[type="text"] + input[type="text"] {
+  margin-top: 10px;
+}
+
 /* List groups */
 .bs-example > .list-group {
   max-width: 400px;