Ability to insert heats.

[Tudor Holton]

We need to provide the ability to add heats before and after existing heats.

The suggestion is that a method be provided such that a heat can be created that is the same as an existing heat which causes a new heat to be created and the original conflicting heat and all heats with a higher number have their heat number incremented by 1.

Suggested UI methods are:
- A additional (small) button before and after each heat; or
- A field to allow people to type a heat number with an "add heat" button.

The second option would have an unintended consequence that a user could create a heat with any number, which may or may not be desirable. A discussion should be had before implementing this feature request.

This is related to bug #309226 and probably more suitable when that bug has been rectified.