Petitboot v1.6.1 tagged

[Samuel Mendoza-Jonas]

Petitboot v1.6.1 has been tagged, including some small fixes and an update to
translations:

- Translation updates
Update translatable languages and fix an issue where wide-character strings
would be truncated in textscreens.

- Fallback to device if snapshot fails to mount
An issue has been noticed occasionally where a snapshot will be created
successfully but fails to mount. This is likely related to the filesystem
being very corrupt and too much of a diff needing to be tracked in the
snapshot. In such a case we fall back to mounting the actual device to ensure
the machine is still bootable.

- Spawn shell in exit handler
When "exiting" Petitboot from the menu instead spawn a shell. This preserves
boot menu changes made by the user, such as custom boot options.