Postgresql auth add bcrypt pw hashing

[asbjorn]

I really don't like storing passwords as plain text in db :)
Also added a section in the README.md file to help users create the SQL tables and also creating hashed versions of the MQTT client passwords.

[wind-c]

I'm a big proponent of hashing passwords.

[wind-c]

There are several problems with your PR:

1. Build failed
2. There should also be go's bcrypt snippet in the README file
3. Have redundant "if err! = nil"

Run go build ./...
go: downloading golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d
go: updates to go.mod needed; to update it:
go mod tidy
Error: Process completed with exit code 1.

[asbjorn]

Hi @wind-c!

Thanks for the feedback - it seems that I forgot the go mod tidy and the redundant iferr checks. There should also be a section in the README file. Also added a link from bcrypt to its corresponding Wikipedia article.

[wind-c]

good job