CSS refactorings and pad-is-not-pinned work

customize.dist/src/less2/include/variables.less

@@ -1,3 +1,9 @@
+// This is a file for generic constants which we didn't want to hardcode everywhere.
+// However, unlike colortheme, customizing these variables will cause breakage.
+
 // Elements size
 @variables_bar-height: 32px;
 
+// Used in modal.less and alertify.less
+@variables_padding: 12px;
+@variables_shadow: 0 8px 32px 0 rgba(0,0,0,.4);