No dedicated way to AOT user namespaces not for export

[timsgardner]

Right now, if you specify user namespaces in configuration.edn with the :export-namespaces key, they will be AOT'd when the AOT menu item is selected (though there is nothing in the documentation to suggest this). However this leaves us without a story for namespaces that should be AOT'd but not exported.

This is pretty urgent, since AOT is of course the only way to avoid paying for compilation on startup.

We need to:

• Provide an option in configuration.edn for AOT'ing user namespaces specifically
• Explicitly document how this process works