Add PackageManifest classes for pypi manifests

Creates PackageManifest class for various python manifests
and overrides the methods for detection and PackageManifest creation.

Signed-off-by: Ayan Sinha Mahapatra <ayansmahapatra@gmail.com>

Author: AyanSinhaMahapatra

src/packagedcode/__init__.py

@@ -76,7 +76,13 @@
     models.MozillaExtension,
     models.ChromeExtension,
     models.IOSApp,
-    pypi.PythonPackage,
+    pypi.PythonMetadataFile,
+    pypi.PythonBinaryDist,
+    pypi.PythonSourceDist,
+    pypi.PythonSetupPy,
+    pypi.PythonDependencyFile,
+    pypi.PythonPipfileLock,
+    pypi.PythonRequirementsFile,
     golang.GolangPackage,
     models.CabPackage,
     models.InstallShieldPackage,