Fill Gap Button with User Defined Values

[AmberSJones]

A user has asked that we enhance the Fill Gap button so that they can use it to fill a gap with values other than -9999. We should discuss whether to implement this functionality.

[AmberSJones]

Also, the technicians are actively working on QC now and for the next 2 months, so we might consider whether we want to devote some development cycles to issues and enhancements that they would immediately used.