0029571: Samples: build qt samples together with OCCT

Extending CMake procedure by 'BUILD_MODULE_QtSamples' variable to switch on qt samples build.
Implementation required:
- union of occt_toolkit_tool.cmake and occt_toolkit.cmake files;
- correction of qt samples sources by adding path to Qt 'plugins' folder. It helps to avoid definition of additional variable (QT_QPA_PLATFORM_PLUGIN_PATH) when staring sample.bat for qt samples;
- executable processing is extended in cmake procedure by providing 'EXECUTABLE_PROJECT' variable. Now we need not specify custom processing for DRAWEXE in occt_toolkit.cmake

samples/qt/Common/src/FILES

@@ -0,0 +1,17 @@
+ApplicationCommon.cxx
+ApplicationCommon.h
+Common-icon.ts
+Common-string.ts
+CommonSample.h
+DocumentCommon.cxx
+DocumentCommon.h
+Material.cxx
+Material.h
+MDIWindow.cxx
+MDIWindow.h
+OcctWindow.cxx
+OcctWindow.h
+Transparency.cxx
+Transparency.h
+View.cxx
+View.h