Modify UC-diagram; Add missing UCs

Added 3 more use cases:
  - "UC - 80 Abstandhalten": It seemed weird that "UC - 70
    Fahrbahn folgen" was considered a use case, but distance keeping
    was not represented in any use case.
    One could consider deleting both use cases.
  - "UC - 90 Kolonnendaten ändern" and "UC - 100 Geschwindigkeit
    ändern" where both added, since the their functionality should not
    be considered part of any other use case, but is essential to the
    project.

Modified associations:
  - Removed PFV from "UC - 50 Kolonne verlassen", since no PFV takes
    action in this use case.
  - Removed FV from "UC - 40 Kolonne beitreten", since no FV takes
    action in this use case.
  - "UC - 10 Status ausgeben" now only has one connection to GV
    instead of one to LV, FV and PFV.

Modified <<include>> and <<extend>> relations:
  - UC - 20 now extends UC - 40, since a platoon needs to be created if
    the first 2 operator want to platoon.
  - UC - 60 now extends UC - 50 for similar reasons.
  - UC - 20 now includes UC - 30.

Added colour coding to the diagram, to group use cases:
  - blue <-> core platoon stuff
  - green <-> input and output of the operator
  - red <-> critical diving

Changed name of "UC - 10"