add sparse matrix support for Protobuf file format
Merge pull request #1670 from gsomix/feature/protobuf

Add sparse matrix support for Protobuf file format
refactor GPs framework
Merge pull request #1676 from votjakovr/feature/gp_refactoring

refactor GPs framework
add arts/asp __init__.py such that it can be imported
fix issue #1611
cleanup svm_binary_classification.ipynb
Dump gmock version to 1.7.0
Fix typo in Serialization_unittest.cc
fix issue #1677: use mathjax in doxygen for displaying mathematical formulas
Add valgrind suppression file when running ctest memcheck
add strange leaking errors of libxml2 to the suppression file