images: add samsung-coreprimevelte

Note: Besides a mediocre feature set, the WiFi is somewhat unstable. Not sure whether that is a blocker for official images. The primary motive for this is being able to advertise the port on XDA (notable because this would be the first publicly released custom ROM for the phone, besides an unstable CM 12.1 build I made some time ago and is not published on XDA anyway).

cc @balejk