Makes the update ChannelManager recognize when a package has been renamed

[evandrocoan]

Makes the update ChannelManager recognize when a package has been renamed, and automatically unmount the previous name and install the new name.

This can be done by just checking the URL.

However, if the URL also changes, then the rename is lost, and the user will have to allow the upgrader to uninstall and install the new package.

For improvement, a update wizard could be created, and the this would present a resume of both upgrades and downgrades. Then allow the user to proceed at once, instead of first upgrading and only later downgrading. This would allow the user by himself to see the package renames the channelinstaler missed.