Use strict array seed

[mvorisek]

merge after: atk4/data#639

no functional change, related with atk4/core#249

[georgehristov]

Why you decided to switch to array only from "class/object or array"?

[mvorisek]

to be exact to "object or array" (i.e. the only required change is to wrap class name/string seeds to an array - if something needs to be changed more, it is more or less bug)

• Because the current design is mixing almost everything and something even the author does not know what to put where.
• These are hidden bugs
• As the seeds are not in a normalized form, a lot of code (maybe 10% of all code) preprocess them "somehow working", but:
  • the behaviours is very inconsistent
  • it is not/can not be tested
  • there are hidden bugs (in preprocessing as well in calls)
  • this extra code can not be maintaned

in the future, there the code can be cleaned up and behaviour can be normalized to clear seed definition (see core/Factory methods)

basically, there should be no specific preprocessing except merging seed with some defaults/forced overrides (passive vs. active merge) and then straight factory call

[DarkSide666]

Another breaking change, but oh well... LGTM