Add Model::writeOrigProblem #62

Job	Run time
doxygen	22s
doxygen	22s
clang_tidy	15s
clang_tidy	33s
clang_format	17s
clang_format	17s
coverage	22s
coverage	16s
test_release_inx (ubuntu-latest)	25s
test_release_inx (ubuntu-latest)	10s
test_release_win	1m 16s
test_release_win	49s
test_release_inx (macos-11)	24s
test_release_inx (macos-11)	21s
test_without_conan	1m 1s
test_without_conan	1m 58s
	9m 8s

Provide feedback