@Jacksonized: modify generated @(Super)Builders such that they will be used by Jackson's deserialization

[janrieke]

This PR implements the proposal discussed here.

Adding @Jacksonized to a context where there is also a @Builder or @SuperBuilder annotation does the following:

1. Configure Jackson to use the builder for deserialization using @JsonDeserialize(builder=MyClass.MyClassBuilder[Impl].class)) on the class. (An error is emitted if such an annotation already exists.)
2. Copy Jackson-related configuration annotations (like @JsonIgnoreProperties) from the class to the builder class. This is necessary so that Jackson recognizes them when using the builder.
3. Insert @JsonPOJOBuilder(withPrefix="") on the generated builder class to override Jackson's default prefix "with". If you configured a different prefix in lombok using setterPrefix, this value is used. If you changed the name of the build() method using using buildMethodName, this is also made known to Jackson.
4. For @SuperBuilder, make the builder implementation class package-private.

There is one minor difference to the proposal (with regard to step 1.): If there is already a @JsonDeserialize annotation on the class, it will give an error. The reason is that all other parameters of @JsonDeserialize are only useful when not using a builder; often they will even contradict the usage of a builder. So I though it is reasonable to error out then and let the user decide what to do.

I did not yet write documentation for the website, because I didn't where to place it (there is no "external" section in the site). I propose adding it as "experimental".

[janrieke]

I pushed two new commits to the branch/PR:

• add flag usage configuration key (I just noticed I forgot this)
• add documentation and changelog entry

[rzwitserloot]

This is amazing work, @janrieke – all I really had to do was think of a funny byline :)