v0.17: improved support of 64-bit logic

- Added 64 bit support for Add and Sub components.
- Added support of some more ATF150x chips.
- Added a register file component.
- Added IC 74273
- Added an "export to zip" function.
- If an input or output has several bits, all pin numbers can be specified by a comma-separated list.
- Now it's possible to choose the polarity of the reset component.
- The model analyzer now creates an error message if a cycle is detected in the circuit.
  This prevents the generation of incorrect truth tables if, for example, a self-built
  flip-flop is analyzed.
- Added a chapter "First Steps" to the documentation.
- Bug fixes
  - Splitter, BarrelShifter and Comparator now are working with 64 bit.
  - fixed a bug in library IC 74198
- Added automated GUI tests. The overall test coverage is now above 70%.