Upgrade Piwik from 1.5.1 to last version

Hello
Guys

Is possible to upgrade piwik version 1.5.1 to 1.7.1 ?
I read the changelogs and there are changes in database on version 1.6, but the last version doesn´t have these changes on database if I understood.

Is there a mirror to download the version 1.6?

Yes possible to upgrade from any version to any later version