Use OpenSSL package & Rootless image

[allir]

To use SSLBump features, switch to debian base image and install squid-openssl package instead.

Updated image to run as proxy user instead of root. The entrypoint script has been updated acordingly.

Entrypoint script also modified to initalize ssl_db in case SSLBump is used.

Logging moved to stdout. Since the process is no longer started by root it enables logging to stdout without issue.

Also added default allow rule for local networks.