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/src/db_repository/README

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+This is a database migration repository.
+
+More information at
+http://code.google.com/p/sqlalchemy-migrate/

backend/flask/src/db_repository/manage.py

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+#!/usr/bin/env python
+from migrate.versioning.shell import main
+
+if __name__ == '__main__':
+    main()

backend/flask/src/db_repository/migrate.cfg

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+[db_settings]
+# Used to identify which repository this database is versioned under.
+# You can use the name of your project.
+repository_id=clpperz
+
+# The name of the database table used to track the schema version.
+# This name shouldn't already be used by your project.
+# If this is changed once a database is under version control, you'll need to
+# change the table name in each database too.
+version_table=migrate_version
+
+# When committing a change script, Migrate will attempt to generate the
+# sql for all supported databases; normally, if one of them fails - probably
+# because you don't have that database installed - it is ignored and the
+# commit continues, perhaps ending successfully.
+# Databases in this list MUST compile successfully during a commit, or the
+# entire commit will fail. List the databases your application will actually
+# be using to ensure your updates to that database work properly.
+# This must be a list; example: ['postgres','sqlite']
+required_dbs=[]
+
+# When creating new change scripts, Migrate will stamp the new script with
+# a version number. By default this is latest_version + 1. You can set this
+# to 'true' to tell Migrate to use the UTC timestamp instead.
+use_timestamp_numbering=False