Update session total popup to use tableformatter
Add row to table by calling tableformatter instance

Make tableformatter instances callable.  The standard way to use a
tableformatter is now:

f=ui.tableformatter(" r l r ")
l.append(f("Field one","Field two","Field three"))
Update session.py tableformatter calls
Update delivery.py tableformatter calls
Update department.py tableformatter calls
Update managestock.py tableformatter calls
Update plu.py tableformatter calls
Update register.py tableformatter calls
Update session.py tableformatter calls (oops, missed one!)
Update stocklines.py tableformatter calls
Update stock.py tableformatter calls
Update stockterminal.py tableformatter calls
Update stocktype.py tableformatter calls
Update user.py tableformatter calls
Update usestock.py tableformatter calls
Update tableformatter API

tableline is now private and should only be created by calling a
tableformatter instance.