Revamping to support workspaces.

Much more work remains to be done, but this is a moderately coherent step.
Codex is now workspace-wide.

This is the first step toward converting many project services to workspace
services. In most cases, we want things to operate across all projects in our
workspace. If I'm looking up a type or opening a file, it could be in any of
the projects in my workspace, so that should be the default operation.
Added addToWorkspace.

Also tidied up and made a note about show-projects.
No longer need to manually add a trailing NL.