Require -r option; Fix broken mount for $HOME in some instances

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
Add support for  ~/.mersdkubu.profile

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
Modify the actual chroot entry invocation to support 12.04's slightly different arg parsing.
Remove old pre-unshare cruft.

Signed-off-by: David Greaves <david.greaves@jollamobile.com>