QmlJS: Add check for duplicated import

Add a soft check for duplicated Qml/JS imports which
adds a warning when a file contains imports that
duplicate the same URI / version or file path.

Change-Id: Ib9a1f8a90dd3cf469d90e83abc1d748901b1e353
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/libs/qmljs/qmljsstaticanalysismessage.h

@@ -43,7 +43,7 @@ enum Type
 {
     // Changing the numbers can break user code.
     // When adding a new check, also add it to the documentation, currently
-    // in creator-editors.qdoc.
+    // in creator-code-syntax.qdoc.
     UnknownType = 0,
     ErrInvalidEnumValue = 1,
     ErrEnumValueMustBeStringOrNumber = 2,
@@ -128,7 +128,8 @@ enum Type
     ErrInvalidStringValuePattern = 320,
     ErrLongerStringValueExpected = 321,
     ErrShorterStringValueExpected = 322,
-    ErrInvalidArrayValueLength = 323
+    ErrInvalidArrayValueLength = 323,
+    WarnDuplicateImport = 400
 };
 
 class QMLJS_EXPORT PrototypeMessageData {