Add support for Conan package manager

Conan (https://conan.io) is a C/C++ package manager, which speeds up the integration of C/C++ libraries into your own project. It's written in Python and available on probably all desktop platforms.

It offers integration into different build systems, e.g. cmake and qmake (https://docs.conan.io/en/latest/integrations/qmake.html). The developer just need to do 3 things: write a conanfile.txt which specifies the needed libraries/packages, add 2 lines to the build system file and call "conan install" before building with the actual build system tool.

Possible features for the conan integration into QtCreator are:

• add "conan install" build step (incl. setting the correct build type and compiler)
• managing the remotes (https://docs.conan.io/en/latest/reference/commands/misc/remote.html)