Adding adding support for custom post-types

[ryanhellyer]

To avoid the need for adding custom code on each site, I added an extra page to provide custom post-type support. Users can simply click a checkbox beside any custom post-type they want to use. By default, it enables the 'post' post-type to match up with the default setup of the plugin.

[gedex]

Hi @ryanhellyer,

Thanks for the PR.

For further PR, can you set your line terminator in your editor to Unix LF only? Right now it's Mac CR. However, I'll rename the add_post_types.php to settings.php