Changes to Linkage and Chain Criteria

[mxgrey]

This pull request addresses issue #437 and replaces pull request #440.

The changes are as follows:

• You can now tell specify in your Linkage Criteria that a start or a target BodyNode should be excluded from the Linkage.
• The new default behavior for Chains is that whichever BodyNode is upstream of the other will be excluded from the Chain
• An alternative constructor is available for Chains which allows the user to request that both the start and the target BodyNodes should be included, regardless of which is upstream
• Linkage and Chain criteria now allow you to specify a nullptr starting BodyNode, which will be treated as if it represents the World

[mkoval]

It looks like the Travis build failed with an obscure Boost error:

[ 37%] Building CXX object dart/CMakeFiles/dart-core.dir/collision/fcl/FCLCollisionNode.cpp.o
In file included from /usr/local/include/boost/numeric/conversion/numeric_cast_traits.hpp:28:0,
                 from /usr/local/include/boost/numeric/conversion/cast.hpp:34,
                 from /usr/local/include/boost/lexical_cast.hpp:159,
                 from /usr/local/include/boost/math/constants/constants.hpp:18,
                 from /usr/include/fcl/BV/RSS.h:43,
                 from /usr/include/fcl/ccd/motion_base.h:45,
                 from /usr/include/fcl/collision_object.h:43,
                 from /usr/include/fcl/collision.h:42,
                 from /home/travis/build/dartsim/dart/dart/collision/fcl/FCLCollisionNode.h:44,
                 from /home/travis/build/dartsim/dart/dart/collision/fcl/FCLCollisionNode.cpp:37:
/usr/local/include/boost/numeric/conversion/detail/numeric_cast_traits.hpp:12:91: fatal error: boost/numeric/conversion/detail/preprocessed/numeric_cast_traits_common.hpp: No such file or directory
     #include <boost/numeric/conversion/detail/preprocessed/numeric_cast_traits_common.hpp>

You didn't change anything in that file, so I don't know what the cause is.

[mxgrey]

It's a nonsense issue that Travis spits out occasionally, possibly because of incorrect installation of boost. It just needs to be rerun.

[jslee02]

👍