Start and End rule values should be stored as BIGINT

Problem/Motivation

Rule entities currently store the start and end values of the first instance, to more easily generate the rest of the recurring values. These are currently stored as standard INT values, which means the database will throw a fatal error if some tries to create a recurring event that starts after 19 Jan 2038.

Proposed resolution

In the same way that the schema was updated for normal field values, update the schema for the rule start an end values.