Improve Python Support (#567)

- Reduce requirements for the python build.
- Fix version number.
- Generate type hints for *.pyi files.
- Make functional for sip-build
- Reduced the unnecessary depth of the package.

NOTE: This is a breaking change for python users, where, `from PyQtAds import QtAds` is changed to `import PyQtAds as QtAds`( or simply `import PyQtAds`)

examples/sidebar/main.py

@@ -5,7 +5,7 @@ from PyQt5 import uic
 from PyQt5.QtCore import Qt, QMargins
 from PyQt5.QtWidgets import QApplication, QLabel, QVBoxLayout, QPlainTextEdit
 
-from PyQtAds import QtAds
+import PyQtAds as QtAds
 
 UI_FILE = os.path.join(os.path.dirname(__file__), 'MainWindow.ui')
 MainWindowUI, MainWindowBase = uic.loadUiType(UI_FILE)