Introduce new flask based python backend

This supports most functionality. Tested the following functionality:
* Create account
* Delete account
* Create a card
* Download offline copy (couldn't log in) - needs work
* Change passphrase
* One time password creation and use

backend/flask/properties/flask.properties.json

@@ -0,0 +1,5 @@
+{
+	"request.path": "../pm",
+	"dump.path": "/dump",
+	"should.pay.toll": "false"
+}