Fix access to static members through instances

[SunBlack]

Changes are done by: run-clang-tidy -header-filter='.' -checks='-,readability-static-accessed-through-instance' -fix

There are some changes I would revert, because they don't increase readability

• QApplication::exec() vs app.exec()
• this->compute_oriented_point_pair_signature => pcl::recognition::ObjRecRANSAC::compute_oriented_point_pair_signature (I believe compute_oriented_point_pair_signature without any prefix is enough)

Whats your opinion? What keep, what revert?

[taketwo]

I certainly like the changes pertaining to numeric_limits and npos. I am not convinced that the rest improves readability, at least for me. But to be honest, I do not really care. Maybe accept all changes just so that in (some undefined) future we can include this check without exceptions at CI.

[SunBlack]

I adjusted a small bit (you can squash commits if you want). So this PR should be fine now.