Read the numbers from a given column and multiply each partial sum
with 10, to go from (0, [1, 2, 3]) -> (1, [2, 3]) -> (10 + 2, [3]) ->
(120 + 3, []) -> 120.
For the first part of day 6 we parse each word on each line as either
a number or as an operator (multiplication or addition). We then order
them all by column and calculate the final value once we have all
numbers and the operator.
Most of the work takes place in the parsing function, the rest is just
summing it all up.
