Hook up removeItem to remove all selected objects

[#82420068] This is working for removal of selected objects and due to
the queing of the UI updates, the performance is quite acceptable, Debug
build on Linux.

Notes:

 1. I have no idea if this is a good way to hook up the collection /
deletion of the selected objects. I did it this way because I know some
tabs have more than one grid view and we will need to collect all
selected objects in one place

 2. Currently, deleting of subrows does not cause a UI refresh. I
attempted to build `develop` and see how the behavior worked there.
However, `develop` doesn't seem to work properly for deleting subrows
either. I will attempt in the next commit to at least have *something*
working.

@evanweaver
Refresh UI on sub-row deletion

[#82420068]

@evanweaver Note: the old code for how rows are deleted is still hooked
up, so if nothing is checked, it deletes the last added row. I wasn't
about to muck with that logic and break things that don't use the grid.
At some point, the logic is going to need to be disconnected for SubTabs
that implement the `selectedObjects()` method.
Fix bug of deleting filtered objects.

Simple typo fix. Without this fix, a filtered - but selected - row will
be deleted by the x even though the user cannot see the row.

[#82420068]