Check for Eigen version

[sjunges]

Errors like

$ cat /Users/Mees_1/storm/build/carl-prefix/src/carl-stamp/carl-build-err.log
clang: warning: argument unused during compilation: '-msse' [-Wunused-command-line-argument]
clang: warning: argument unused during compilation: '-msse2' [-Wunused-command-line-argument]
/Users/Mees_1/storm/build/resources/3rdparty/carl_download/source_dir/src/carl/core/rootfinder/EigenWrapper.cpp:3:10: fatal error: 'eigen3/Eigen/Dense' file not found in #include <eigen3/Eigen/Dense>

seem to originate from using a wrong preinstalled eigen version. It would be helpful to detect such errors during configuration to clarify that this is a problem with the host system. We could e.g. check whether the include compiles (cmake has some nice functions that support these checks).