Fix all() not working with plugins.

Make all() actions delegate to main() which in turn correctly configures
the plugin properties.

Refs #4135
Fix broken options in FixtureTask.

The options in FixtureTask were not as comprehensive as they needed to
be. Previously the records flag was overloaded to do 2 jobs. It signaled
that you wanted to pull records from the live table, and if schema was
present that you wanted to import records at runtime. It was not
possible to express a fixture that imported schema, but pulled records
in from the live table at time of generation.
Add missing subcommand definition.

Without this it was impossible to run `bake fixture all` :(
Fix help text for fixture all.
Merge pull request #4144 from cakephp/issue-4135

Fix plugin option missing on all, and add missing option on fixture task