Change start parameters or ExtrapolationCell to be unique_ptr (was ACTS-362)

Original author Andreas Salzburger @asalzbur

The start parameters of the ExtrapolationCell have been stored as const reference, however, if the ExtrapolationCell is moved out of the scope where the startParameters are constructed, they can run out of scope - BAD.

Edited Mar 27, 2019 by Moritz Kiehn

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information