WEB-12534 Code completion overriding emmet

- recalculate completion on prefix changing if there are no template and empty
prefix
- allow css-emmet templates in the start of style-attribute value

xml/impl/src/com/intellij/codeInsight/template/emmet/ZenCodingTemplate.java

@@ -548,6 +548,9 @@ public class ZenCodingTemplate extends CustomLiveTemplateBase {
           }
         }
       }
+      else if(result.getPrefixMatcher().getPrefix().isEmpty()) {
+        result.restartCompletionOnPrefixChange(StandardPatterns.string().longerThan(0));
+      }
     }
   }
 }