Marketplace improvements

Some features that really would benefit Arastta's marketplace (in no particular order)

- Allow developers to create coupons on the extension store. It should allow
--- Select a specific customer to use it, all previous purchasers of a certain coupon, or anyone. If its easier, allow a CSV based list of either usernames or purchaser e-mails
--- Select the number of uses in total. No customer should ever need a coupon more than once, but when anyone can use a coupon it will need a limit really
--- Select a specific product, or all products (of the current developer only)
--- Have a start/end date
--- Allow fixed discount or percentage

- Allow customers to rate the developers support as well as the extension, and show this on extension pages and the developer page

- Allow a developer to set if purchasers should be notified of an update. Sometimes you may just want to update an extensions details and not notify the customer of the edit. Other times you add new files and the customer should be notified of this. It would be nice if we could have an optional message box of what can be sent to the customers

- Add in a bit more information on the fields that aren't in the opencart extension store. For example the field for "Your message to the reviewer". I'm not entirely sure what this is for to be honest. Does this get sent to the reviewer before/after they review

- Allow to either upload larger images (as the ones at the moment are far too small when clicked on - just like OpenCarts) or allow a developer to add external images to the list, and just make a thumbnail from that

- Allow a developer to add more information on their developer page - ie text content/links to their own support

- Remove the "latest" from the market place home screen. This will end up having the same abuse that OpenCarts store did, where people were deleting extensions and recreating them so that they were visible on the home page. I'd recommend just having a "Arastta staff picks" and random extensions on the home page. The one OpenCart has now with the recently updated is similarly open to abuse, where people "update" their extensions daily making no actual change just to get on the front page

- Allow a developer to see all the order history for a transaction, and notify them if there is a change. This may or may not already be in place, but its definitely something that needs to be there