Add support for pagination methods equivalent to those in the Redactor plugin #350

Description

Sorry, this is only a bug in that it broke when attempting to migrate across from the Redactor plugin but I wasn't sure where else to raise it.

The Redactor plugin includes the methods:

• getPage
• getPages
• getTotalPages

The only documentation I could find for these is here, but these methods still work with the latest (and now abandoned) version of the Redactor plugin. It would be great if they were also supported in the CKEditor plugin in order to simplify migrating over.