Fixed build problems mainly for Windows and Visual C++
Created by: Neurochrom
Tested on Visual C++ 2017 (15.3) Community Edition, boost 1.65.1, OpenSSL 1.1.0, Cmake 3.9.3 - everything builds, but not all tests pass yet. Some additional minor changes are:
- additional comments,
- stdout error messages in http(s) examples,
- POST method examples,
- a .gitignore that ignores the build directory.