[SofaTest] Add Backtrace::autodump to all tests

[damienmarchal]

As requested by @matthieu-nesme in #149
(but what is the xml ?)

---

This PR:

• builds with SUCCESS for all platforms on the CI.
• does not generate new warnings nor unit test failures.
• does not break existing scenes.
• does not break API compatibility.
• has been reviewed and agreed to be transitional.
• is more than 1 week old.

Reviewers will merge only if all these checks are true.

[matthieu-nesme]

@damienmarchal, I am talking about these xml files:

[ RUN      ] BilateralInteractionConstraint_test/1.attributesTests
bash: line 1:  2202 Segmentation fault      build/bin/SofaConstraint_test --gtest_output=xml:build/tests/SofaConstraint_test/report.xml 2>&1

(copied from https://ci.inria.fr/sofa-ci/job/centos_clang-3.4_options/262/console)

But I think @guparan is working on the subject.

[guparan]

Did not have time to start this yet. 😢
As discussed last wednesday, the idea would be to simply cat the output of crashed tests during the print-summary() phases (for unit tests and scene tests). So only scripts stuff.

[damienmarchal]

So let Guillaume finish...
But is the autodump stuff useful or not ?
If Backtrace is not installed by default how a failing test will print anything ?