Implement WordPress codesniffing

[JohnRDOrazio]

I haven't used any linting until now. Perhaps the time has come to start creating standards, so that the coding style follows a given and expected style. Seeing that WordPress has implementing it's own set of linting rules, we should probably follow those as closely as possible seeing this is a WordPress plugin.

There are a few rules that I really like compared to the PSR-12 standards, such as:

• spaces after opening parentheses and before closing parentheses

There are just a few rules here and there that I don't quite agree with, and I'm going to disable them:

• disallowing short array syntax (really?)
• enforcing a trailing comma on the last item of an array

[JohnRDOrazio]

Currently being handled in the oop-dev branch.