Initial moveable cells functionality.
Tests for moveable cells.
Fix true|false bug.
Make cell_moved on_cell_moved to conform to on_cell_deleted.

Also checks for the method and warns the user.
Change edit? to edit_mode?
Moar specs! 🙀
Fix failing tests.
Allow the user to restrict the cell's movement within a section.
Implement @silasjmatson's idea about moving move_cell into promotion_table_data
Fix conflicts, bring up to date with master
Merge pull request #570 from clearsightstudio/reorderable

Reorderable table screen cells