Export ol.View2D.prototype.constrainCenter function
Add an extent constraint to the device-orientation example
Add constrainCenter documentation
Merge pull request #2019 from fredj/device-orientation-example

Add an extent constraint to the device-orientation example
Give Somaliland and Northern Cyprus unique ids
Do not make ol.style.Image exportable

Application developers should use its subclasses.
Merge pull request #2115 from tschaub/duplicate-id

Give features unique identifiers.
Merge pull request #2116 from ahocevar/no-imagestyle

Do not make ol.style.Image exportable
Move workshop reference to doc index
Merge pull request #2120 from bartvde/workshop

Move workshop reference to doc index