AutoTest: Test execution from result output pane

Enable test execution via context menu in the result output pane.
At the moment only gtest is supported.

Task-number: QTCREATORBUG-16695
Change-Id: Ib39164c3cb44d249647b11e25dc51c9ac5db89c5
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/autotest/testrunner.h

@@ -55,6 +55,7 @@ public:
     ~TestRunner();
 
     void setSelectedTests(const QList<TestConfiguration *> &selected);
+    void runTest(TestRunMode mode, const TestTreeItem *item);
     bool isTestRunning() const { return m_executingTests; }
 
     void prepareToRunTests(TestRunMode mode);