Use "get" prefix for configuration attribute getters

[laudrup]

The configuration-as-code plugin expects a plugins configuration attributes to be accessible with setters prefixed with "set" and getters prefixed with "get" or "is".

Change and add the getters for the configurations attributes that don't follow this convention so this plugin can be fully configured with configuration as code.

A test has been added that ensures that all configuration methods with a "set" prefix has a corresponding "get" or "is" prefix. This is similar to how the configuration as code plugin does it.

I have not created a related issue for this, but the issue is that this plugin is not fully configurable with configuration-as-code which is unfortunate. I will of course create a related issue if this is required.

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- [x] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[laudrup]

Turns out an issue was already created for this. This commit fixes #321