add DBR::Config::Instance::Anon to talk about instances before metadata is fully set up
move table prefix/qualify logic to Connection
allow instatiating DBR without immediately configuring
refactor DBR::Sandbox to use anon instances and deferred DBR configuration instead of talking directly to SQLite
Major hacking to allow running tests on MySQL

Because I want to make sure migrations stuff works on multiple databases.  Test
schemas are now written with a few abstractiony bits, including TBL(xxx) for
table qualification/quoting and Q(xxx) for identifier quoting.  PRIMARY KEY NOT
NULL is not accepted by MySQL and is redundant in any case.  Use AUTOINCREMENT;
the underscore will be added for MySQL.  Also fixes the datetime type to work
on MySQL.

To use this, run the test suite after setting:
DBR_SANDBOX_INSTANCE_FACTORY='mysql_factory,<host>,<user>,<pass>'
actually test prefix lengths
whoops, forgot the dbr_schema_mysql files
some initial tests for the alter phys-migration
structural validations for phys-alter.  let it be tentatively decided that dbr-migrate uses moose.