Implementation Types should be displayed in a drop down list

In the current version, the implementation types are displayed in a read only text box, and the user can go through them by clicking on "Previous" and "Next" buttons. They should be displayed in a drop down list.

NOTE: I tried putting them in a drop down list but I noticed that the option list is not rendered correctly, and it doesn't change its position if I move the pin (and with it, the bubble).