Remove Legacy Extrapolation (was ACTS-538)

Original author Andreas Salzburger @asalzbur

The Propagation/Extrapolation is in a stage that we can remove the legacy extrapolation from acts-core.

This will simplify the geometry code immensely, the testing of Acts vs Trk can also be done in the context of ATLAS now.

Edited Mar 27, 2019 by Moritz Kiehn

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