Further little improvements for Cantor-Zassenhaus.
added final_states to Gray-code transducer, improved docstring
Constructed Gray code now also has correct final states.

Commit 1efa597519da1fa32436e0e1e2dddf609cca391b sets final states
for transducers.GrayCode. These were also incorrectly set in
the example in finite_state_machine.py. This is now fixed. The doctests
now also check whether final and initial states of the Gray Code
transducers agree.
Corrected link from transducers.GrayCode to example in finite_state_machine module
changes in Gray-code example

- some spacings
- srange instead of range
- new doctests
- inserted wiki-link
Merge remote-tracking branch 'origin/u/cheuberg/fsm/example_gray_code' into u/cheuberg/fsm/example_gray_code

* origin/u/cheuberg/fsm/example_gray_code:
  Corrected link from transducers.GrayCode to example in finite_state_machine module
  Constructed Gray code now also has correct final states.
Merge remote-tracking branch 'origin/u/dkrenn/fsm/example_gray_code' into fsm/operator_transducers-on-beta8

* origin/u/dkrenn/fsm/example_gray_code:
  changes in Gray-code example
  Corrected link from transducers.GrayCode to example in finite_state_machine module
  Constructed Gray code now also has correct final states.
  added final_states to Gray-code transducer, improved docstring
  Gray code example modified and prepackaged transducer
  finite_state_machine: Add an example on the Gray code into the documentation

Conflicts:
	src/sage/combinat/finite_state_machine_generators.py
corrected one doctest and added another (left-shift transducer)
Bad construction of the 600-cell
trac #2686 good construction of the 600-cell
trac #2686: Two embeddings for the 600-cell graph
trac #2686 last details
trac #2686 adding the 120-cell graph
trac 2628: An embedding for the 120-cell
Trac 10963: attempt at improving the wording for quotients/subquotients
switch left<->right; expand explanations

- Renamed the shift_left_tranducer to shift_right_transducer, because
it actually was a right shift.
- Explained the right shift (as opposed to the left shift which
  would be reasonable at first sight)
- Changed DocTest for enforcing last digit zero in order to
  include a first digit zero to make it clearer what we actually check.
- Explain None in xor_transducer with earlier explanation.
- Enhance DocTest of xor_transducer to show what None does.
- Additional Doctest for xor_transducer
- explain construction of transducer in more detail, more links
- link to generators.GrayCode
Merge branches 't/16132/fsm_process_output_new-on-beta8', 't/16138/fsm/is_complete', 't/16140/e5f4b5b06c8936ba80c86b5431f7cce194c90b94', 't/16143/fsm/example_gray_code' and 't/16144/fsm/cartesian-product-intersection-additional-example' into base/16145
Merge branch 'base/16145' into t/16145/ticket/16145
Removed reference to HKW2014 from FiniteStateMachine.final_components

[HKW2014] is cited both in FiniteStateMachine.final_components and
in FiniteStateMachine.asymptotic_moments. Only one of them can be a
label, so the other one had to go. Not sure whether this is the
correct way, but so errors are avoided.
replaced one new instance of raise E, V by raise E(V) (cf. #15990)