Inform users in case of incompatible RulesMode configuration

[britter]

In the settings script, users can configure the global behavior for capability rules via dependencyResolutionManagement.rulesMode. This property can have three values and depending on that this plugin needs to behave differently:

• RulesMode.FAIL_ON_PROJECT_RULES and base plugin not explicitly applied via settings: fail the build.
• RulessMode.FAIL_ON_PROJECT_RULES and base plugin explicitly applied via settings: do not apply base plugin on project.
• RulesMode.PREFER_SETTINGS and base plugin not applied via settings: fail the build.
• RulesMode.PREFER_SETTINGS and base plugin applied via settings: don't apply the base plugin on project.
• RulesMode.PREFER_PROJECT always apply base plugin on the project no matter if it has been declared in settings already.