scalesboard_weight_avoirdupois; minor icon cleanup
core numpad, respect entry size even on keyboard
algebra_by, accept on more digit in the entry

Thus if the anser is 9 the children may enter 2 digits.
scalesboard, added support for the numpad
core numpad, made the number smaller

the numbers rectangles are smaller but the touch area are twice of them.
it is also possible to set the number's width with the columnWidth
property.
scalesboard, smaller numpad buttons