[+] add parameter to include tests for dashboard

CellFrameDashboard.pro

 TEMPLATE = subdirs
-SUBDIRS = CellFrameDashboardGUI CellFrameDashboardService \
-    CellFrameDashboardTests
+SUBDIRS = CellFrameDashboardGUI CellFrameDashboardService
 
 CellFrameDashboardGUI.subdir = CellFrameDashboardGUI
 CellFrameDashboardService.subdir = CellFrameDashboardService
@@ -16,3 +15,8 @@ unix: !mac : !android {
     share_target.path = /opt/cellframe-dashboard/share/
     INSTALLS += share_target
 }
+
+BUILD_DASHBOARD_TESTS {
+    message(BUILD_DASHBOARD_TESTS enabled)
+    SUBDIRS += CellFrameDashboardTests
+}

CellFrameDashboardTests/gtest_dependency.pri

 isEmpty(GOOGLETEST_DIR):GOOGLETEST_DIR=$$(GOOGLETEST_DIR)
 
-message("_PRO_FILE_PWD_" = $$_PRO_FILE_PWD_/../../3dparty/googletest)
-
-
 isEmpty(GOOGLETEST_DIR) {
     warning("Using googletest src dir specified at Qt Creator wizard")
     message("set GOOGLETEST_DIR as environment variable or qmake variable to get rid of this message")

CellFrameDashboardTests/main.cpp

-#include "tst_settings.h"
-
 #include <gtest/gtest.h>
 
 int main(int argc, char *argv[])