Cleanup error handling of cbmc/ folder#2703

Merged

NlightNFotis merged 3 commits intodiffblue:developfrom

NlightNFotis:develop_cbmc_cleanup_rebase

Sep 4, 2018

Commits on Sep 4, 2018

Convert assert calls to INVARIANTs

hannes-steffenhagen-diffblue
authored and
NlightNFotis
committed
Implementation of a erroneous user input exception class.
NlightNFotis
committed
Change the unstructured asserts to invalid_user_input_exceptions and preconditions/invariants.
NlightNFotis
committed