Configure proj4 options and transforms upon construction

[ahocevar]

This makes it easier to add additional configuration options to projections that are connected to a proj4js definition.

Previously (still works):

var proj = ol.proj.get('EPSG:1234');
proj.setExtent([1, 2, 3, 4]);

Now:

var proj = new ol.proj.Projection({
  code: 'EPSG:1234',
  extent: [1, 2, 3, 4]
});

The difference when using this new approach is that additional properties will not be set on the projection instance that is returned from the registry when using ol.proj.get():

> var proj = new ol.proj.Projection({code:'EPSG:1234',extent:[1,2,3,4]});
> ol.proj.get('EPSG:1234').getExtent();
null
> proj.getExtent();
[1,2,3,4]

[elemoine]

Would it make sense to change the examples that currently use setExtent?

[ahocevar]

Good point. I'll do that.

[ahocevar]

Would it make sense to change the examples that currently use setExtent?

Done @elemoine.

[elemoine]

This looks good to me.