Fixes for windows

[maxGimeno]

• Fixes the pthread dependency as discussed in Search for pthread or pthreadVC2 lib in CMakeLists #428
• Fixes the boost dependency declaration in libpointmatcherConfig.cmake.in so the users won't have to declare it in their project.

I also have a bug, that says that yaml-cpp-pm-targets.cmake cannot be found, and I have to manually copy it from /build/contrib/yaml-cpp-pm/CMakeFiles/Export/share/libpointmatcher/cmake/ to ./build but I couldn't find how to fix it.

Fixes #435

[ethzasl-jenkins]

Can one of the admins verify this patch?

[pomerlef]

ok to test

[pomerlef]

Thanks for the PR!

@peci1 anything breaking on your side before I merge?

[peci1]

Thanks for asking, this looks harmless ;)