for DoDecay()

make Event non-templated, store index instead of StackIterator

HStackView as drop-in replacement for SecondaryView

started testHistory with HStackView

renamed HStackView to HSecondaryView

Include proposal process rebase

Closes #2

See merge request AirShowerPhysics/corsika!245

Merge branch 'include_proposal_process_rebase' of gitlab.ikp.kit.edu:AirShowerPhysics/corsika into include_proposal_process_rebase

Consider the types of the different coordinate systems when calculating the momentum. Not using scoped enumeration because static_cast is required to specify the tuple position. Instead mark variable with an extra letter 'e' and use it only very scoped.

Remove proposal from cascade example, improve error message.
Improve output, and shower diagnostics: hunting all the energy Produce REAL error message.