Add support to connect a column to another table

For example, a user could have their weekly TimeTable set with columns as timings and rows as days. Each course-slot could show the subject code, which can trigger a dialog which specifies more details about the course (from another table), on clicking.

The issue describes linking a timetable column or cell to records in another table and showing course details in a dialog, but it names no files, tests, or entry points. First inspect the table and dialog implementation and clarify the intended data relationship and interaction. Done means the linked records can be selected or activated from a table view and their details appear consistently.

Written by the indexing model from the issue text.