Refactor DiceParser

[Vlek]

One thing that I have been mulling over is a refactor for the DiceParser
anyway that would allow me to remove a considerable amount of reused
boiler plate code. We have the initial get-left-hand-value and then the
for-loop that then allows us to use the next operation and
left-hand-value, but that means then that we should make functions to
handle those operations and use it inside of a helper method that does
that heavy lifting only in one place.