In this release I've added a fix for the levelup string, as well as added some requested features:

• Already tamed wolves can become a Dog by interacting with it - Requested by @Victor13
• Untame your dogs without killing them! /mydog free <id> - Requested by @Minestick
• Configurable option for Dogs to not teleport between worlds - Requested by @Minestick and @Daddy_Spin
• Configurable option for Dogs to only show their nametags when hovering over them - Requested by @Minestick

Thanks for all your valueable feedback, you guys are really helping making this plugin what it is <3