Rephrase "snapshot" to "backup"

[buhtz]

Back In Time (BIT) does use the term "snapshot" in the GUI, CLI and documentation. The term will be rephrased into "backup".

Reason:

• Term "Backup" is more appropriate and pointing technical to what BIT is doing.
• Snapshot might be understood by some people as an image of the file system.

This happens after discussing this on the mailing list. https://mail.python.org/archives/list/[email protected]/thread/R7RJDJIW5IPXX4MBDBS44U2UROROZO57/

[daveTheOldCoder]

I formerly used rsnapshot, which is a Perl script based on the rsync command. I switched to BackInTime because it's similar but has a GUI, so I don't have to manually edit a text configuration file.

Maybe that's where the term "snapshot" originated?

But changing the term to "backup" is reasonable.