Fix plist version setting script.

Some paths were broken; we now do that after we compile, and do it in
the build install directory.
Fix checkout bundles task in debug configuration.

Before it tried to rsync the bundles, but the part that actually fetched
the bundles didn't run in the debug configuration, so the rsync step
failed because the directories were never created.
In snapshot configuration, never optimize.
Switch the default build to snapshot mode.

We do want things like the textmate bundle copies to happen.