Use Eigen for math operations

[jslee02]

This PR switches to Eigen for the math operations as suggested (#96).

The goal of this PR is to pass all the unit tests with equal to or better than the previous computational performance, and it seems it's achieved as of now. Other possible improvements (e.g., the templatizing suggested by @sherm1 (comment)) might be done in a separate PR.

Here are several todos that will be done in this PR:

• removing repetitive conversion between quaternion and rotation matrix
• utilizing lazy evaluation
• utilizing aliasing

Edit: Above todos will be done in future PRs to keep this PR as simple as possible for code review.

[traversaro]

Some minor comments on the CMake parts of this PR, that can be probably fixed in other PRs .

• There is any specific reason to use a custom pkg-config based FindEIGEN3.cmake rather then to copy FindEigen3.cmake officially distributed by Eigen [1]? I always had bad experience in using pkg-config in Windows, especially regarding path with spaces. I also suggest to integration the modification proposed in this PR [2], so if there is a Eigen3Config.cmake available in the system we use the information provided by the config file.
• The Eigen3 headers directories are include at directory level with a #include_directories(${EIGEN3_INCLUDE_DIRS}), but given that Eigen3 headers are include in the public headers, we need to populate the INTERFACE_INCLUDE_DIRECTORIES of the exported fcl target. We can do that by calling target_include_directories(fcl PUBLIC ${EIGEN3_INCLUDE_DIRS}). Note that this will result in a non-relocatable fclConfig.cmake, but this can be solved in future PRs I think.

[1] : https://bitbucket.org/eigen/eigen/src/8267656b597c03c7fe501be33056cda9a63e88ab/cmake/FindEigen3.cmake?at=default&fileviewer=file-view-default
[2] : https://bitbucket.org/eigen/eigen/pull-requests/213/modify-findeigen3cmake-to-find/diff

[jslee02]

Thanks for the comments! I just didn't know that there is an officially distributed FindEigen3.cmake. Could we apply the proposed modification once it gets merged, though? Just in case it's updated with some feedbacks.

[traversaro]

Yes, it makes sense to adopt the changes in FindEigen3.cmake only when they are adopted upstream.

[sherm1]

Eigen conversion looks great, @jslee02. Very nice to see files get deleted!

[peterkty]

Just a note that
setQuatRotation(), setTranslation() for transformation are no longer available after the conversion.
Transform3f was a quaternion plus translation. Now it is just a 3x3 matrix.
Vec3f is now Vector3f

I'm compiling moveit_core and it throw out these compile error.

[jslee02]

For completion: Vec3f is actually Vector3d. The scalar type of Vec3f was FCL_REAL, which is double, as Vector3d is.