Support comparisons with more than one relation

[rkaminsk]

TODO:

• [x] add support for extended comparisons and adjust unit tests
• [x] remove CSP extension
  • I decided to remove the extension as part of this PR because refactoring would have been too involved
• [x] add support for extended comparisons in AST
• [x] update Python API and its unit tests
• [x] add additional unit tests especially in view of pool handling
• [x] open an issue to port clingox to changes
• [x] Visual C++ 2017 (wrongly) complains about a default move constructor
  • annotating more move constructors noexcept should make this error go away