Update architecture documentation

The architecture docs are very dated, and have several references
to tenants, PAM backends, and controllers that don't exist.

Change-Id: I85de743006e7df4fcf8ddbc3afc1a4bcd69583e6
Adding an index on token.user_id and token.trust_id

This is a performance update to ensure that we are scanning the fewest
number of rows on a user delete (causing token revocations). Without
these indexes it is possible to scan all valid tokens, causing
significant overhead, to find the user or trust matching tokens.

Due to selecting the extra column (needed for other matches in
some cases) this can also cause issues with buffer pool sizes.

Change-Id: I202b5c87a221d8dba99d16b0a1baa7546fef093b
Closes-Bug: 1332666
Clean up the Configuration documentation

Lots of lines that were well over 80 characters; several code
examples were missing code-block syntax. General inconsistencies
between what is actually available vs. what is documented.

Change-Id: I726e13aa7c333973cf92bbe1550b939c634db493
Fix failure of delete domain group grant when identity is LDAP.

When deleting a domain group assignment while using a non
domain-aware backend, such as LDAP, an AttributeError was being
raised when trying to find all the relevent tokens. This was due
to a hang over from when you had to pass domain scope to
list_user_in_group(). This only affected domain group grants,
by luck we got away with it for group project grants.

Change-Id: I47b61886698232a7d3dfb4b502d61723cb0eb786
Closes-Bug: 1373113
New section for CLI examples in docs

In an effort to make 'configuration.rst' less bloated, move
common cli examples to their own section. Changed the titling
so they are no longer subtitles of another section.

Change-Id: I2785cbe8563e5adcae65aebf88152a5e055c28a9
Merge "Adding an index on token.user_id and token.trust_id"
Merge "Fix failure of delete domain group grant when identity is LDAP."
Merge "Clean up the Configuration documentation"
Merge "New section for CLI examples in docs"
Merge "Update architecture documentation"