A system for storing and distributing MySQL permissions.

Requires tlslite (http://trevp.net/tlslite/).

Permissions are stored in Python format using a set of permissions definition
tools (define.py). They are parsed and expanded into permissions table SQL
by use.py. This expansion step is complex, because the definition step allows
negative permissions (grant SELECT on this database, but not on this table
within it), which MySQL doesn't support natively.

Once converted to SQL, permissions may then be pushed to the database. The
push process interacts directly with the mysql permissions tables, then calls
FLUSH PRIVILEGES. It does not use GRANT/REVOKE.

In addition to direct push support, the system supports permissions
distribution to alternate tables in an admin database, which are modified
copies of the mysql tables. See permissions.sql for SQL to create these
tables. This allows multiple permissions sets to be stored in the database.
For example, the table could contain primary and replica permissions sets.
Both sets are published to the primary, and some tool then copies them from
the admin tables to the mysql tables on each MySQL server, using use.py:Copy().

permissions file -----push----> mysql tables
                 \               ^^ copy ^^
                  +--publish--> admin tables

WARNING: These tools make it much easier to break permissions on all of your
MySQL instances at once. They will happily copy out bad permissions, or no
permissions. Proper use of push_duration may mitigate this, but take care to
implement appropriate safety checks for your environment.