Yes you have to uninstall 7.0.6 first. If you then install 7.0.12 into the exact same directory (it will be preserved during the uninstall), all your settings and data will be imported during the install process.
No you do not have to install all of the inbetween versions.
Follow the guide here for more detailed steps. http://kb.tableausoftware.com/articles/knowledgebase/upgrading-tableau-server