Spelling issues in hamiltonian_cycle()

[jdemeyer]

Reported by eviatarbach in #9698 (relating to the files sage/graphs/generic_graph.py and sage/graphs/generic_graph_pyx.pyx):

1. All instances of "hamiltonian" should be changed to "Hamiltonian". This is because Hamilton is a proper noun, and the capitalization transfers to the term (see here:  http://mathworld.wolfram.com/HamiltonianCycle.html). "hypohamiltonian" should be left lower-case, though.

2. "neccesary" should be "necessary"

3. "non hamiltonian" should be "non-Hamiltonian" (note the dash)

4. "Dodecahedral" should not be capitalized; "dodecahedral"

5. "Running the algorithm on random instances, just to make sure the answers are still satisfiable path". Should be "paths".

6. "ajacent" should be "adjacent"

7. "Now, we try the algorithm on a non hamiltonian graph, the Petersen graph" should be "graph: the".

8. "another known hypohamiltonian graph, the generalized Petersen" should be "graph: the"

[knsam]

Let me just confirm the work issues: we don't want the changes to affect the function names, right? Should this change affect the error messages?

~KnS