Upgrade and downgrade instructions

To upgrade MailerQ from version < 5.2 to 5.2+

Debian/Ubuntu:

sudo apt update
sudo apt install -y mailerq
sudo mailerq --repair-database

CentOS/RHEL:

yum update
mailerq --repair-database

To downgrade MailerQ from version 5.2+ to 5.1

Debian/Ubuntu:

sudo apt-get install -y --allow-downgrades mailerq-5.1 mailerq=5.1.1
sudo mailerq --repair-database

CentOS/RHEL:

yum remove mailerq-5.2
yum install mailerq-5.1
mailerq --repair-database