Redo line-height globally

- Rename -height to -height-base to match other vars
- Drop use of -height across the board and rely on it to be inherited
- Adjust padding of .dropdown-header to account for different line-height of h6 heading element (this needs refactoring for variables and rems also)

scss/_pagination.scss

@@ -47,7 +47,6 @@
   float: left; // Collapse white-space
   padding: $pagination-padding-y $pagination-padding-x;
   margin-left: -1px;
-  line-height: $line-height;
   color: $pagination-color;
   text-decoration: none;
   background-color: $pagination-bg;