Remove remaining code from spynnaker8

[Christian-B]

This removes the last of the code from the spynnaker8 directory.

Changes include.

spynnaker8 is no longer being documented.

spynnaker8 init file moved to spynnaker.pynn
spynnaker8.external_devices init moved to spynnaker/pyNN/external_devices
spynnaker8.extra_models moved to spynnaker/pyNN/external_devices

The above three files replaced with redirect hook files which will war in Version 7 and error in 8
spynnaker8 init will detect if it is called by import spynnaker8 or import pynn.spinnaker
- in the first is warns that a change is needed
- in the second it runs setup_pynn and errors asking to run again

added
spynnaker.pynn.setup_pynn
- note could not be under just spynnaker as the the import pyNN gets confused

Code that was deprecated in version 6 will now error.

abstract_spinnaker_common.py has been merged into spinnaker.py
spinnaker.py also moved to spynnaker/pyNN

abstract_spinnaker_common.py has been replaced with a redirect hook for the one static method called elsewhere.
test with http://apollo.cs.man.ac.uk:8080/blue/organizations/jenkins/Integration%20Tests/detail/remove_8/6/pipeline
(which was before upstream changes pushed)

spynnaker8/utilities/neo_convertor.py one method in deprecated class did not log. It now errors.

tests changed to moved stuff

Note: the original spynnaker8 setup_pynn I an unsure about.

• Currently left to make it easier to switch back to the spynnaker8 way of doing things
  I suggest doing that in a later PR but before the release

--
These PRs adapt to the removal of abstract_spinnaker_common.py
Note: global_data_new_pr do it a different way so these are only needed if that is refused.
SpiNNakerManchester/sPyNNakerNewModelTemplate#84
SpiNNakerManchester/SpiNNGym#42

tested by:
#1163