Issue 23: Added progress indicators and cancellation (#34)

- Wrapped all table operations in a new foreground job context, which mediates foreground tasks.
- Added cancellation support and partial results for table read operations.
- Added the "mark" command, which can mark, unmark & toggle marked items
- Added support for alias arguments.
- Removed the "unmark" command, and replaced it as an alias to the "marked" command
- Fixed seg faults raised when there is no table shown in the result set.

internal/dynamo-browse/ui/teamodels/colselector/model.go

@@ -48,11 +48,11 @@ func (m *Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.compositor.ClearOverlay()
 	case controllers.ColumnsUpdated:
 		m.colListModel.refreshTable()
-		m.subModel = cc.Collect(m.subModel.Update(msg))
+		m.subModel = cc.Collect(m.subModel.Update(msg)).(tea.Model)
 	case tea.KeyMsg:
 		m.compositor = cc.Collect(m.compositor.Update(msg)).(*layout.Compositor)
 	default:
-		m.subModel = cc.Collect(m.subModel.Update(msg))
+		m.subModel = cc.Collect(m.subModel.Update(msg)).(tea.Model)
 	}
 	return m, cc.Cmd()
 }