Add support for custom popup on BondsTable

[disberd]

This PR adds support for custom popups on BondsTable rows.

It will fix #14

The idea is to also create a custom function similar to fielddata and fielddescription that can be used to add methods for specifying popups for the custom fields.

A default popup template will also be defined that is applied to all fields of the struct, so one must only modify the general template for the intended type if a general custom behavior is desired (not different per field)