Basic keyboard accessibility CSS tweaks

Mostly doubling-up :hover styles to also cover :focus, as a first step
to making the framework more keyboard-friendly.
Additionally, fixed two small markup issues in the docs/examples to
make the "Learn more" large primary button-styled links
keyboard-focusable (as without href they're treated as non-tabable
anchors).

less/pagination.less

@@ -32,6 +32,7 @@
   border-left-width: 0;
 }
 .pagination ul > li > a:hover,
+.pagination ul > li > a:focus,
 .pagination ul > .active > a,
 .pagination ul > .active > span {
   background-color: @paginationActiveBackground;
@@ -43,7 +44,8 @@
 }
 .pagination ul > .disabled > span,
 .pagination ul > .disabled > a,
-.pagination ul > .disabled > a:hover {
+.pagination ul > .disabled > a:hover,
+.pagination ul > .disabled > a:focus {
   color: @grayLight;
   background-color: transparent;
   cursor: default;