Hey,
after a couple of horrible weeks of trying and googling and getting angry about the documentation/complexity, I finally figured it out. Therefore I decided to make a complete tutorial on how to include an external third party library into unreal and use their functions.
Before that, I have to complain to the Unreal developers a bit: First of all, the complexity of the code and the amount of boiler-plate code one needs is quite high. Furthermore, the documentation and also the error messages don’t help very much solving the problems (at least regarding plugin creation). For the future, I’d like to encourage you to reduce the code complexity / amount of boiler-plate code and to improve the documentation.
Anyhow, here is the Tutorial on my blog:
A boost / PCL plugin template to be used as a starting point can be downloaded here: