Restore script, PBKDF2, and dependency updates

[EnigmaCurry]

Thanks very much for this script, I've been hacking on it for the past few days. I've got some updates you may wish to re-incorporate in your branch. Sorry, they're all here in one branch together:

• Updates to alpine 3.15
• Updates to postgresql14-client
• Makes new restore script (fixes #7)
• Introduces common.sh for parts common to both backup and restore
• Turns on PBKF2 key derivation.

Before turning on PBKF2 I was seeing this warning (and now with this patch is absent):

2022/01/22 03:09:00 12: *** WARNING : deprecated key derivation used.
Using -iter or -pbkdf2 would be better.

[EnigmaCurry]

I just now see theres other open PRs for the restore feature, I don't mean to step on anyones toes.