Allow --create-db to be passed along to sql-sync; insure that settings.php is rewritten in transitional site record

Use 'integrate' mode instead of 'interactive' when calling updatedb, and save status messages printed during updatedb. Factor out stages and mappings to separate files.

Use drush_invoke_process instead of drush_invoke to download Drupal. Fix up 'integrate' settings for all calls to drush_invoke_process.

Assume that a missing 'ok' state transition should go to the next sequential state in the fsm. Remove all trivial state transitions (most of them). Nice.

Fix some problems that crept in to the re-use code case; bring back some code accidentally removed in the last commit.

Fix problem from previous commit: remapped projects could not be found. Force the upgrade to exit if pm-enable fails.

Order extensions so that no extension will ever be upgraded prior to its dependencies being upgraded.