Explicitly set UpdateTime to update to current time on a change to the row

[gregcorbett]

In MySQL 5.1,

The first TIMESTAMP column in a table, if not declared with the NULL attribute or an explicit DEFAULT or ON UPDATE clause, is automatically assigned the DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP attributes.

In MySQL 5.6.6+ (the version used for Indigo DataCloud), this does not happen.

No TIMESTAMP column is assigned the DEFAULT CURRENT_TIMESTAMP or ON UPDATE CURRENT_TIMESTAMP attributes automatically. Those attributes must be explicitly specified."

See here for the MySQL documentation referring to this.

This PR explicitly specifies NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP for all columns called UpdateTime, and provides an update_schema.sql file to upgrade any existing databases. Any NULL time stamps will be set to CURRENT_TIMESTAMP when update_schema.sql is applied.

Once this PR is applied, UpdateTime will now explicitly update on 5.6.6+ as it does on implicitly on 5.1

[tofu-rocketry]

Looks fine.