Use OpenLayers 2.13.1 in examples.
No warnings when building docs.

This adjusts the documentation so that the current JSDuck 5.2.0 doesn't
issue warnings.
Merge pull request #189 from marcjansen/doc-fixes

No warnings when building docs.
Merge pull request #188 from marcjansen/ol-2.13.1-examples

Use OpenLayers 2.13.1 in examples.