Make accessibility features editable

[joedolson]

Is your feature request related to a problem? Please describe.

Currently, the accessibility features are stored in a way that makes them very difficult to extend or modify. It would be beneficial to end users if they could edit the features to better meet their needs, by renaming, adding more, or even removing.

Describe the solution you'd like
Users should be able to add or edit the available accessibility features

Accessibility features should be searchable & filterable in event views.