QmlJS checks: Suppression of static analysis messages.

* Use '// @disable M123' to suppress
* Add quick fix to add these comments

Change-Id: I499f5a6004148afbb346218c6fb01c9ca77b9f73
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>

src/libs/qmljs/qmljsstaticanalysismessage.h

@@ -122,6 +122,8 @@ public:
     bool isValid() const;
     DiagnosticMessage toDiagnosticMessage() const;
 
+    QString suppressionString() const;
+
     AST::SourceLocation location;
     QString message;
     Type type;