I don't think any of them use the nonlin ortho camera estimate anymore

Just test it locally after we're done.

Also move adding -pthreads to examples/CMakeLists.txt, this will eventually have to be modernised as well

Replaced C++ compiler check logic and replaced the eos custom target with an INTERFACE library target

At the moment this doesn't make the headers show up in IDEs - we'll deal with it later.

CMake should fail on the gcc-4.8 build.

Enabling GENERATE_PYTHON_BINDINGS on travis