Switch from dotted notation style classes to   Payment_Ewayrecurring style

I recently went through building a new processor & determined with @totten that the preferred class naming for module extensions is CRM_Core_Payment_Ewayrecurring with the db entry extensions being Payment_Ewayrecurring

I've been having a bunch of problems with this on different versions & the 'half-way-between-old-an-new' seems to be a major part of it - this PR switches to what I understand as the recommended way.

However, I'm not sure that on 4.2.x the upgrade functions ran - I might check with Tim if he expected they would. Would appreciate any testing anyone feels able to do....