Break out drush make calls in a new platform install task

This *must* be split in separate tasks, because we are now using drush make to actually install platform instead of just importing existing ones.

This is especially important for proper rollback procedures, which are impossible to do in the current scenario, as I found out in #1081536: Platform verify doesn't rollback apache config file.

subbing

How would this split work?

Would the frontend task actually call three separate tasks, provison-save, provision-build (?) and then provision-verify instead of the two currently?

Something still has to call make right? So what would that be?

Right I see..we want to catch things like: #1081536: Platform verify doesn't rollback apache config file and roll back before we ever generate the platform config files, and the trick is we need to know when this is a platform that we're verifying for the first time, or one that's been verified before and now doesn't verify.