/**
* The ol.proj namespace stores:
* * a list of {@link ol.proj.Projection}
* objects, one for each projection supported by the application
* * a list of transform functions needed to convert coordinates in one projection
* into another.
*
* The static functions are the methods used to maintain these.
* Each transform function can handle not only simple coordinate pairs, but also
* large arrays of coordinates such as vector geometries.
*
* When loaded, the library adds projection objects for EPSG:4326 (WGS84
* geographic coordinates) and EPSG:3857 (Web or Spherical Mercator, as used
* for example by Bing Maps or OpenStreetMap), together with the relevant
* transform functions.
*
* Additional transforms may be added by using the {@link http://proj4js.org/}
* library (version 2.2 or later). You can use the full build supplied by
* Proj4js, or create a custom build to support those projections you need; see
* the Proj4js website for how to do this. You also need the Proj4js definitions
* for the required projections. These definitions can be obtained from
* {@link http://epsg.io/}, and are a JS function, so can be loaded in a script
* tag (as in the examples) or pasted into your application.
* The first time there is a request for a projection, either with a
* {@link ol.proj.projectionLike} or directly with {@link ol.proj.get}, the
* code will check if the Proj4js library and the necessary definition are
* loaded; if so, it will register the appropriate {@link ol.proj.Projection}
* object and add transform functions between the new projection and all the
* existing ones. See examples/wms-image-custom-proj for an example of this.
* Because the check for presence of the Proj4js library and the definition only
* takes place on the first request for them, this means they can be loaded
* dynamically as needed; for example, with user-supplied data where you don't
* know in advance what projections are needed, you can initially load minimal
* support and then load whichever are requested.
*
* Note that Proj4js does not support projection extents. If you want to add
* one for creating default tile grids, you can add it after the Projection
* object has been created with `setExtent`, for example,
* `ol.proj.get('EPSG:1234').setExtent(extent)`.
*
* In addition to Proj4js support, any transform functions can be added with
* {@link ol.proj.addCoordinateTransforms}. To use this, you must first create
* a {@link ol.proj.Projection} object for the new projection and add it with
* {@link ol.proj.addProjection}. You can then add the forward and inverse
* functions with {@link ol.proj.addCoordinateTransforms}. See
* examples/wms-custom-proj for an example of this.
*
* Note that if no transforms are needed and you only need to define the
* projection, just add a {@link ol.proj.Projection} with
* {@link ol.proj.addProjection}. See examples/wms-no-proj for an example of
* this.
*
* @namespace ol.proj
*/