This directory contains Axyl database patch scripts. These are named in
a specific format:
  upgrade_P.Q.R_to_X.Y.Z.sql
  
  example: 'upgrade_2.1.0_to_2.1.7.sql'

The varying parts of this are P.Q.R which represents the old version of
the schema the patch is being applied to, and X.Y.Z which is the version
of the schema that the database will be compliant with after the patch.

Note that we expect these patch files to be contiguous, and therefore
to enable upgrading from any version to any final version up to and
including the HEAD version at any time.

These patch scripts are applied by the following shell script which is
normally run by the Debian postinst script:

 AXYL_HOME/install/upgrade-axyl-databases.sh

