Add /repo/import functionality to the API (BB-15090)

I recently dealt with a use-case for a fairly large product I work on which required me to use the API BitBucket provides to automate not only creation of a lot of private repositories but also duplication of a number of them. I found the API lacking in latter functionality. I discovered the /repo/import functionality on the Web which was exactly what I wanted but not on the API. After having explained my use-case and requirement on a support ticket, I was asked to create a request here. If this is something more people would use, I'd like to request the devs to consider it for a moment.

Thanks.