Documentation for exported object literals

This adds the infrastructure that we need for documenting
exported object literals. This is best done by using *.jsdoc
files, which are parsed by JSDoc but not the Closure Compiler.
In addition to adding the documentation of the objects literal
properties, the respective namespaces must also be annotated.

Restricting the API docs to the exported API will be added as a
separate pull request.
Correct typos in objectliterals.jsdoc
Use objectliterals.jsdoc instead of objectliterals.exports
Merge pull request #497 from openlayers/doc-objectliterals

Documentation for exported object literals