[REVIEW] 261 - Improve dropdown menu exhibition

[KiSobral]

Description

This PR focus on improving the user experience on the page that selects exhibitions. Doing so, we corrected and changed a few classes to resolve the problem.

Resolves (Issues)

resolve #261

General tasks performed

• Create ListTextWidget class
• Improve ExhibitForm class
• Improve exhibit_select method by adding new forms
• Delete unused code

Have you confirmed the application builds locally without error? See here.

• [x] Yes