add support for fcl 0.6

[2scholz]

The (still unreleased) fcl 0.6 changed paths to relevant headers as well as the name of many types.
This patch adds support for fcl 0.6 without breaking support for fcl 0.5.

This patch adds the header fcl_compat.h to check for the fcl version and include fcl headers accordingly.
The old types are exchanged to the newer ones throughout the package.
Compability to fcl 0.5 is ensured by creating type aliases that map the old types to the new ones.

The other way around might be the better choice for now, but the old type names are still in use in the new versions (as templates), so the alias trick only works this way around.

For this a lot of code from @Levi-Armstrong was used, who already created a branch with support for fcl 0.6 but without support for fcl 0.5: https://github.com/Levi-Armstrong/moveit/tree/newFCL

@v4hn

[BryceStevenWilley]

A third option, besides aliasing old types to new or new types to old types, is to using typedefs that are not in the fcl namespace. This is the approach taken by OMPLapp (ompl/omplapp@b986838#diff-524e09a932cb1946ad510acbcd23bec5R56). This does make it more difficult to keep up with additions to FCL itself however. Both require lots of small changes in the codebase as well.

As long as we agree on how to handle the aliases, this is a great contribution. . 👍

[v4hn]

I asked @2scholz to implement it the way he did and we discussed quite a bit while he worked on it.

I believe it would be better to merge this only after the FCL maintainers pushed a release tag to their repository. That way we can refer to their officially released API for the way we use it here.

However, if they don't manage to do this reasonably soon, I'm also happy with merging it right away.

[rhaschke]

Including all headers in fcl_compat.h reduces compiler performance and should be avoided.
I suggest the following:

• Define a macro FCL_VERSION_CHECK to simplify version checking:

  #define FCL_VERSION_CHECK(major, minor, patch) ((major<<16)|(minor<<8)|(patch))
  #define FCL_VERSION FCL_VERSION_CHECK(FCL_MAJOR_VERSION, FCL_MINOR_VERSION, FCL_PATCH_VERSION)```
  

• In fcl_compat.h provide class forwards to get rid of includes, but allow typedefs:

  namespace fcl {
  class CollisionGeometry;
  using CollisionGeometryd = fcl::CollisionGeometry;
  ...
  }
  

• Restore individual includes, explicitly switching between old and new using the introduced macro:

  #if (FCL_VERSION >= FCL_VERSION_CHECK(0, 6, 0))
  #include <fcl/narrowphase/collision.h>
  #else
  #include <fcl/collision.h>
  #endif
  

[rhaschke]

I agree to merge this before an official FCL 0.6 release. Backwards-compatibility is ensured ;-)
Please rebase.

[2scholz]

I made the requested changes.
FCL_VERSION is already defined in fcl/config.h, so I named the macro MOVEIT_FCL_VERSION instead.