Currently there are various UIs for associating sources and/or Javadoc with binary roots, according to project or
library type. Inevitably there are special cases which do not cleanly fit into any of these UIs, or the UI is hard to
discover or requires too much clicking.

A user will most commonly encounter the lack of such an association when using the editor - primarily in the code
completion popup, but perhaps some other places as well, e.g. Javadoc window. I suggest that at this time, if no
association of either kind can be found, an SPI be consulted whereby modules could offer the ability to form
associations that would take effect immediately. Example impls (in lookup order):

1. apisupport.project could add associations for a module JAR part of some platform. (Not applicable to module
Class-Path extensions.)

2. project.ant could offer to make associations for a shared library, optionally copying source/Javadoc to the lib folder.

3. project.libraries would offer to make associations for a known global library.

4. project.libraries could offer to create a placeholder global library for an arbitrary binary JAR and then proceed as
in #3.

UI could be something like a hyperlink in the popup Javadoc window. E.g.

---%<---
No source code or Javadoc is known to match this compiled class.
<More Info>
<Create Library...>
---%<---