This allows to infer names of options from their names in a configuration. CamelCase is translated into snake_case automatically when `apply` is triggered.
* Don't have all `RuleConfiguration`s conform to `InlinableOptionType`. Mark types that must have this capability explicitly. Same for `AcceptableByConfigurationElement`.
* A type being an `InlinableOptionType` doesn't mean it's automatically inlined. This also doesn't depend on the fact of having a name for its key configured any longer. Instead, an `inline` attribute must explicitly be set to `true` in `@ConfigurationElement`.
* Key name inference is optional and can be overwritten by specifying a key name in the attribute.
* Inlined configurations only fail in `apply` when they are really sure that something is odd. Otherwise, they accept to not being updated.
With the binding of configurations to their associated rule types
"unknown configuration" errors can be made more specific mentioning
also the rule's identifier in the printed message.
Danny Mösch
JP Simard