use CVODES error string instead of numeric flag in error messages

[yizhang-yiz]

This PR addresses #1039 by replacing flag with strings from CVODES.

Summary

The replacement happens inside the checking functions. With added cvodes_check we call the library functions that map flag to error string constant.

Tests

All CVODES unit tests with error throw checks.

Side Effects

na

Release notes

More informative error messages for ODE solvers.

Checklist

• Math issue Add better error handling for CVODES #1039.

• Copyright holder: Metrum Research Group

  By submitting this pull request, the copyright holder is agreeing to the license the submitted work under the following licenses:
  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested

[yizhang-yiz]

@syclik do you want to take a look of this one?

[yizhang-yiz]

@wds15 would you like to review it? thx

[stan-buildbot]

---

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
gp_pois_regr/gp_pois_regr.stan	3.58	3.55	1.01	0.86% faster
low_dim_corr_gauss/low_dim_corr_gauss.stan	0.02	0.02	1.0	-0.38% slower
eight_schools/eight_schools.stan	0.09	0.09	1.01	0.54% faster
gp_regr/gp_regr.stan	0.15	0.14	1.04	3.65% faster
irt_2pl/irt_2pl.stan	5.74	5.77	0.99	-0.55% slower
performance.compilation	92.78	90.76	1.02	2.18% faster
low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	8.03	8.11	0.99	-0.96% slower
pkpd/one_comp_mm_elim_abs.stan	32.76	29.99	1.09	8.45% faster
sir/sir.stan	120.09	122.12	0.98	-1.69% slower
gp_regr/gen_gp_data.stan	0.04	0.03	1.04	3.6% faster
low_dim_gauss_mix/low_dim_gauss_mix.stan	3.04	2.98	1.02	1.89% faster
pkpd/sim_one_comp_mm_elim_abs.stan	0.41	0.38	1.08	7.64% faster
arK/arK.stan	2.07	2.08	1.0	-0.35% slower
arma/arma.stan	0.23	0.23	1.01	0.74% faster
garch/garch.stan	0.58	0.57	1.01	1.37% faster
Mean result: 1.01923991221

---

Jenkins Console Log
Blue Ocean
Commit hash: ee568be

---

Machine information

ProductName: Mac OS X ProductVersion: 10.11.6 BuildVersion: 15G22010

CPU:
Intel(R) Xeon(R) CPU E5-1680 v2 @ 3.00GHz

G++:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix

Clang:
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix

[yizhang-yiz]

This is ready for review. @SteveBronder @rok-cesnovar any of you have time for this? It's a straightforward impl.

[rok-cesnovar]

Overall I think this is a great improvement of the current state. Thanks @yizhang-yiz!

I commented in a few spots that things could be slightly improved.

[rok-cesnovar]

Looks great. Will probably take a day or a few to get Jenkins tests to pass again. Merge whenever the green light is back.

[yizhang-yiz]

thanks a lot @rok-cesnovar

[stan-buildbot]

---

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
gp_pois_regr/gp_pois_regr.stan	3.59	3.54	1.01	1.4% faster
low_dim_corr_gauss/low_dim_corr_gauss.stan	0.02	0.02	0.97	-3.49% slower
eight_schools/eight_schools.stan	0.08	0.09	0.99	-1.22% slower
gp_regr/gp_regr.stan	0.14	0.14	1.01	0.8% faster
irt_2pl/irt_2pl.stan	5.7	5.82	0.98	-2.05% slower
performance.compilation	92.97	90.96	1.02	2.16% faster
low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	8.03	8.04	1.0	-0.16% slower
pkpd/one_comp_mm_elim_abs.stan	32.11	31.01	1.04	3.44% faster
sir/sir.stan	121.28	117.04	1.04	3.5% faster
gp_regr/gen_gp_data.stan	0.03	0.03	0.97	-2.74% slower
low_dim_gauss_mix/low_dim_gauss_mix.stan	3.01	3.16	0.95	-5.15% slower
pkpd/sim_one_comp_mm_elim_abs.stan	0.39	0.38	1.02	2.3% faster
arK/arK.stan	2.06	2.05	1.0	0.49% faster
arma/arma.stan	0.23	0.23	1.0	0.35% faster
garch/garch.stan	0.58	0.58	1.01	0.76% faster
Mean result: 1.0008438709

---

Jenkins Console Log
Blue Ocean
Commit hash: 74c37fd

---

Machine information

ProductName: Mac OS X ProductVersion: 10.11.6 BuildVersion: 15G22010

CPU:
Intel(R) Xeon(R) CPU E5-1680 v2 @ 3.00GHz

G++:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix

Clang:
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix