Enhance CakeMethodAlias and CakePropertyAlias to allow passing a version number

https://github.com/cake-build/website/issues/426 raised the issue that it is not visible on the website with which version a specific feature was added. An easy way to improve this situation would be to enhance `CakeMethodAlias` and `CakePropertyAlias` with the possibility to pass a version string which represents the version in which the alias or property was introduced. On the website we can read and display this information.

Locate the definitions of CakeMethodAlias and CakePropertyAlias and trace how the website consumes their metadata. Determine how a version string can be passed for an alias or property, then verify that the website can read and display the introduction version.

Written by the indexing model from the issue text.