One step event registration

[xcf33]

We will need to convert the event registration process into a one step form very much the same way as the donation feature.

We will use commerce custom line item to achieve this. The only difference is that we will create a new field in the event content type that will store different paid event registration levels. This field could be a textarea that works like a selection widget entry KEY | LABEL.

We will also need to clean up the interna/external event type and just change it to "registration option", [free, paid, no registration]. If paid registration is selected, it will show the textarea to enter registration levels for that event.