fix: ERC725X and ERC725Y inherit Ownable first

[mattgstevens]

This solves a solc compile error TypeError: Linearization of inheritance graph impossible by inheriting the "most base-like" contracts first to prevent errors from inheriting contract.

See a similar fix here OpenZeppelin/openzeppelin-contracts#1128

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I came across this issue with a contract that has a token implementation from OpenZeppelin and ERC725Y as part of its inheritance graph.

[mattgstevens]

ping @frozeman as you seem to be the only recent commiter to this repo.

[frozeman]

we just moved everything to a new structure with core contracts as abstracts, can you please test if the issue still exists in this one?
If not we might need to move the ownable around here contract ERC725Y is ERC725YCore, Ownable {

[mattgstevens]

@frozeman just tried it out, and its the same error since the refactoring did not change the ordering of inheritance.

updated this PR to make the changes on the latest master

[mattgstevens]

FWIW after a refactoring that removed inheriting Ownable directly this is no longer an issue, as only ERC725Y pulls it into the inheritance graph (and so the ordering issue is gone).

Still think this is a good change to land, following the reason given in the first comment, as this can be a confusing error to receive from solc.

d