separate paste-deploy configuration from parameters

PasteDeploy configuration contains class names which might change
between releases. Keeping it separate from user-configurable
parameters allows deployers to move paste-deploy ini file out of
configuration directory to a place where it can be safely overwritten
on updates e.g. under /usr/share/

DocImpact

Change-Id: I9292ca6226c8430b93565dedd45cc842742a23e2
Replace assertDictContainsSubset with stdlib ver

Code copied and adopted from unittest.TestCase class from CPython 2.7
stdlib.

Change-Id: Ifae16f947600f7a9d1f8d1a879fd914d0cf4d65e
Merge "separate paste-deploy configuration from parameters"
Add index on expires column of the SQL token Backend

Add migration script to add the index.

bp index-token-expiry

Change-Id: I36934c18979df5037d606d4846b29194750847af
Fixes: bug #1168399