#70 Add bootstraps for the EquipmentModel CRUD

1. Addition of bootstraps for the EquipmentModel CRUD
2. Alteration of the validation of uniqueness of EquipmentModel name
3. Addition of feedback messages for the controller actions in EquipmentModel and EquipmentType 
4. Correction in @Unique annotation now it can be placed in parameters too
5. Addition of a cancel button in the form, so it can go back to the list of the current crud