Function for auth_token middleware config

Each project was configuring the auth_token middleware using several
lines of inisets. Since all the projects should configure the
auth_token middleware in the same way create a function and call it.

Change-Id: I3b6727d5a3bdc0ca600d8faa23bc6db32bb32260
Configurable token hashing algorithm

The Keystone server and auth_token middleware were enhanced to
support a configurable hash algorithm.

With this change, the user can set

 KEYSTONE_TOKEN_HASH_ALGORITHM=sha256

in their localrc to use the SHA256 algorithm rather than the
default md5. Any hash algorithm supported by Python's hashlib can
be used. The MD5 algorithm doesn't provide enough protection from
hash collisions and some security standards mandate a SHA2 hash
algorithm.

Change-Id: I8b373291ceb760a03c4c14aebfeb53d8d0dfbcc1
Closes-Bug: #1174499
Merge "Function for auth_token middleware config"
Merge "Configurable token hashing algorithm"