CMake and added functionality

[hochshi]

Hi,
I've used fgt to create pyfgt a simple pybind11 python wrapper around fgt.

Unfortunately, the local FindEigen3.cmake is unable to find Eigen3 when used when through pip or conda build systems. So, I've added an option (WITH_EIGEN_NOMODULE) that allows users to use find_package(Eigen3 3.1 REQUIRED NO_MODULE) and link against Eigen3 instead of find_package(Eigen3 3.1 REQUIRED). I haven't messed about with FindEigen3.cmake since I'm unaware of the reasons for it's creation and proper usage.

The second addition has to do with easier usage in Coherent Point Drift, where having the entire matrix instead of weighted sums is considerably faster and easier.

[gadomski]

Thanks for the contribution! I'd like to know more about why pip/conda can't use the current FindEigen3.cmake -- if possible, I'd prefer to fix the find script, rather than add a new configuration option. Can you post information here or in a new issue re: the find script breakages?

Also, for the new functionality, can you add one or more tests demonstrating correct functionality? Thanks!

[hobu]

Thanks for the contribution! I'd like to know more about why pip/conda can't use the current FindEigen3.cmake -- if possible, I'd prefer to fix the find script, rather than add a new configuration option. Can you post information here or in a new issue re: the find script breakages?

I think the better thing to do is to use CMake's own config machinery like I have implemented in #54.

[gadomski]

Closing as OBE by #54