Merge some functions in the import process, and clean up a type from earlier. is_writable not is_readable

#343428 - move to proc_open, instead of exec, which makes the serialization parsing rock solid. Also, we can now pass an optional array to the calling script, which will allow us to not pass sensitive information over the command line

#343428 - better serialized string protection. not perfect due to weirdness in how exec handles spaces before newlines. Will need to switch to proc_open to fix this

Experimental update.php for DRUPAL 5. This is not integrated into any drush commands or the hosting front end yet

Replacement provision_invoke function which is a lot cleaner and simpler than the old one. It now automatically does pre_task, task and post_task variations, and handles rollbacks correctly across the whole set. This means broken site installs now roll back correctly.

moved the drupal installation process into it's own php process, to avoid cross db issues. much simpler now.

Fixed on-demand module loading. Add pre_verify and post_verify hooks. Added a script which clears existing drupal caches to allow new modules that have been enabled etc, to be picked up

(backport from head)

See: #338657

Add provision_exec to run external provision scripts in their own namespace. This is the basis of a cleaner install task

Add provision_exec to run external provision scripts in their own namespace. This is the basis of a cleaner install task