Commit 2f976576 added default setup dep
handling to the existing install command code paths, but unfortunately
broke the handling for the new-build code path. It added a call to
addDefaultSetupDependencies into the standardInstallPolicy. That
interfered with the addDefaultSetupDependencies that ProjectPlanning was
already using.

So this patch splits a basicInstallPolicy out of standardInstallPolicy,
where the basicInstallPolicy is all the old stuff, and the
standardInstallPolicy just adds the addDefaultSetupDependencies that the
install/fetch/freeze commands need. So then ProjectPlanning uses just
the basicInstallPolicy.

The 2f976576 commit also added a new and simpler method to determine if a
package has had default setup deps added. Previously ProjectPlanning had
to use a rather complex method to remember this information. So this
patch removes all that and makes use of the new method.

To stop this breaking in future the next patch adds integration tests to
cover custom setup script handling.

This fixed issue #3394.