[Finishes #59857934] Adds CRUD controls for Instruments.

This Pull Request merges the manage_instruments branch into the release-0.3.1 branch.

This was a feature requested by Kelly via email so that she can add data that is missing from the CMS dataset and which Natalie Epler will be sending via email. This was a quick task to do as the model is very similar to the Designations. Since it prevents the data from being inputted I believe that it could be added directly to release-0.3.1.

The pull request adds:

* CRUD controls for Instruments. 
* link to Instruments index from the topbar menu
* Adds validations in instruments model
* Adds specs for managing instruments