This commit simplifies the exports.js plugin so it only relies
on the stability notes to generate the documentation, which
completely decouples it from the exportable API.
As a rule of thumb, whenever something has an 'api' annotation,
it should also have a 'stability' annotation. A more verbose
documentation of ol3 specific annotation usage is available in
the new 'apidoc/readme.md' file.
This commit also modifies all source files to implement these
usage suggestions.
