Add update + join support.

This currently only works in MySQL. Additional work will be needed to
make it work with postgres + sqlite.
Fix failing test.

Columns were removed from the fixtures in a previous set of changes.
Update this test to reflect that.
Add basic table level updates.

Add basic table level updates that can update multiple records. Don't
implement _matchRecords or other join workarounds as they often lead to
concurrency issues. We can revisit that functionality later on if
necessary.
Rename method to match 2.x method.

update() is a handy method that I don't want to use just yet.
Add update with join support for Postgres.

Postgres requires some query fudging to make joins with updates
syntactically valid. Add a query translator that moves joins around and
creates a 'from' clause.
Enforce consistent ordering

Fix cross DB test failures caused by ordering and cross join issues.
Refactor and clean up.

Add early returns and reduce complexity of methods.
Add update + join support.

This currently only works in MySQL. Additional work will be needed to
make it work with postgres + sqlite.
Merge branch '3.0' into 3.0-table-update

Conflicts:
	lib/Cake/Database/Query.php
	lib/Cake/Test/TestCase/Database/QueryTest.php
	lib/Cake/Test/TestCase/TestSuite/TestFixtureTest.php
Fix typo that was causing tests to fail.
Merge pull request #1360 from markstory/3.0-table-update

3.0 table update
Merge remote-tracking branch 'origin/3.0' into feature/cleaner-query
Fixing problem with fixtures in different connection objects