Utils/all: Move mime constants into a central place

They are reasonably standardized, and generally usable cross-plugin,
so this can help to avoid a few cross-plugin compiletime dependencies.

Change-Id: Icb2b010c3e12dee69df54ab16f6f8e90d9cffba6
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qmlprojectmanager/qmlproject.cpp

@@ -28,6 +28,7 @@
 
 #include <utils/algorithm.h>
 #include <utils/infobar.h>
+#include <utils/mimeconstants.h>
 #include <utils/process.h>
 #include <utils/qtcassert.h>
 
@@ -44,7 +45,7 @@ using namespace Utils;
 namespace QmlProjectManager {
 
 QmlProject::QmlProject(const Utils::FilePath &fileName)
-    : Project(QString::fromLatin1(Constants::QMLPROJECT_MIMETYPE), fileName)
+    : Project(Utils::Constants::QMLPROJECT_MIMETYPE, fileName)
 {
     setId(QmlProjectManager::Constants::QML_PROJECT_ID);
     setProjectLanguages(Core::Context(ProjectExplorer::Constants::QMLJS_LANGUAGE_ID));