Feature request: Add support for batch editing

[magico]

There are times where I need to edit dozens or even hundreds of items at the same time. For example, updating a specific column to true for many instances at a time. It would be amazing if madmin supported this.

[excid3]

Definitely would like to do batch actions.

We can add checkboxes to the rows and a dropdown above of actions. Submitting one of those would send over the IDs or an all value of some sort to the matching action.