Fix rule plugins

[daledavies]

• Moves creation of rule instance objects from rule_checker into rule_instances_controller.
• Renames configurable interface to instance_configurable and introduces a new plugin_configurable interface, allowing plugins to implement their own "global" settings.
• Fixes a few issues and errors found in some rule plugins.
• Addresses issue #46.

I'd probably recommend reviewing this commit by commit, rather than all at once.

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@phager-at Just need to fix the failing checks and it'll be back over to you.

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All done 😃

[phager-at]

I've added some more thoughts about general architecture, as I wasn't able to work on it while you implemented your last changes (roughly 2 weeks ago).

TL;DR:

• I still think using interfaces as a form of contract to ensure our implemented features would be good. There'd be solutions for the constructor problem.
• We should think about including the instance configuration (other) in the constructor, as it's part of the "configurable instance" feature and should be set via setter defined in the instance_configurable interface.
• Related to the other-setter suggested above, it may be advisable to implement all this in a builder/factory, so the builder/factory can then call all the relevant feature related setters and methods during construction of the rule object

[daledavies]

I think I have a solution that satisfies all your feeedback so far.

• Re-introduce the rule_interface
• Move getter and setter for instance config to instance_configurable interface
• Remove rule_base class entirely
• Use a rule_trait trait so rule plugins don't have to implement the basics every time
• Use a factory method to do validation and return a constructed instance object.

Now we hopefully have the best of both worlds, interfaces for everything and rule plugin definition can still be quite simple.

Just tidying up and I'll push as a new commit so you can see the difference.

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I'm not too pleased with so many getters and setters, but I guess that's a failing of PHP. Maybe one day we can use property hooks or something!

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@phager-at As mentioned above, I've taken your suggestions into account and reworked things in the latest commit. Hopefully this is better, I'm certainly happier with it - thanks for your advise.

Back over to you :)

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Rebased to fix conflicts now main has been updated.