Remove unnecessary format subclass methods

[rjgildea]

Remove unnecessary __init__ and _start methods from Format classes:

• There is no need for every subclass to redefine the __init__ method and
  call its parent's __init__ method. As well as a lot of unnecessary code
  duplication, this also led to the subclass self.understand() method
  being called once for every class in the format class hierarchy.
• There is no need for every subclass to redefine the _start() method and
  call its parent's _start() method.
• Use super() where applicable.

[graeme-winter]

Reviewing...

[graeme-winter]

0-th order - tests:

Master:

Results (47.73s):
     504 passed
       1 xfailed
      15 skipped

Branch:

Results (117.56s):
     503 passed
       1 xfailed
      15 skipped

Interesting that there were fewer tests 🤔 possibly one added since you made the branch. Time difference due to nproc= for first not second 🙄

[graeme-winter]

Looked through the changes (after the first few, scanned diffs) and they look fine.

Tests pass effectively the same before and afterwards. No evident regressions.

=> 👍

[graeme-winter]

I should also say: this is a good thing and will help newer developers as there is (slightly less) cargo culted nonsense in there.

[rjgildea]

Interesting that there were fewer tests 🤔 possibly one added since you made the branch.

@Anthchirp split one test into two here which probably accounts for the differing number of test compared to master: dials@8c169ff

[Anthchirp]

I now removed one on master, so count should be identical again 😏