Qt module project structure (#124)

Refactor the project structure to make it build as a "Qt module". It's a first step to get this tool closer to Qt.

The main advantage here is: Simply running:
```
qmake
make
make install
```

will compile and install the tool into your Qt installation, and make it a part of your Qt just like any other tool (qmake, etc.)

tests/tests-ci.sh

@@ -10,8 +10,8 @@ mkdir -p linuxdeployqt.AppDir/usr/bin/
 cp /usr/bin/patchelf /usr/local/bin/{appimagetool,mksquashfs,zsyncmake} linuxdeployqt.AppDir/usr/bin/
 find linuxdeployqt.AppDir/
 export VERSION=continuous
-cp ./linuxdeployqt/linuxdeployqt linuxdeployqt.AppDir/usr/bin/
-./linuxdeployqt/linuxdeployqt linuxdeployqt.AppDir/linuxdeployqt.desktop -verbose=3 -appimage
+cp ./bin/linuxdeployqt linuxdeployqt.AppDir/usr/bin/
+./bin/linuxdeployqt linuxdeployqt.AppDir/linuxdeployqt.desktop -verbose=3 -appimage
 ls -lh
 find *.AppDir
 xpra start :99

tests/tests.pro

@@ -0,0 +1,11 @@
+TEMPLATE = subdirs
+
+SUBDIRS += \
+	QtQuickControls2Application \
+	QtWebEngineApplication \
+	QtWidgetsApplication
+
+DISTFILES += \
+	tests-ci.sh \
+	tests-environment.sh \
+	tests.sh