Ensure v2 tokens are correctly invalidated when using BelongsTo

Due to the optional paramater of the tenant on several v2 token
validation methods, we need to ensure that calling token validation
with different permutations of parameters does not lead to an incorrect
cache value being returned.  This is done by lifting the 'BelongsTo'
checks out of the token backend and into the Manager, in a layer above
where the token caching takes place.

Fixes bug 1226225

Change-Id: Ifa3162923ad41aac6a9e5d5b4996bc43dc9b11fb
Rewrite README.rst

Most of the content in the README is unmaintained and out of date, and
can be replaced by references to documentation that *is* more properly
maintained.

This patch replaces most of the contents of the README with
low maintenance links.

Fixes-Bug: 1227734
Change-Id: I4d63d971f94329197bd7001682d0d655901457f0
Monkey patch select in environment

Explicitly say what needs to be monkey patched in
environment/__init__.py. By doing this we are making the code easier to
read and select needs to be monkey patched in order for notifications to
work with keystone/openstack/common/rpc/impl_qpid.py. Without monkey
patching select, keystone will hang on sending a notification since
qpid_messaging won't operate properly when establishing a connection
with the qpid broker.

Change-Id: I4cbdf29924473a76ce459d969e5e7077aac5beb8
Closes-bug: #1224565
Merge "Ensure v2 tokens are correctly invalidated when using BelongsTo"
Merge "Monkey patch select in environment"