Beans: put ExportName on fields (goodbye to strict JavaBeans)

[ljacqu]

Goal: base bean properties on a class's fields (that have getters/setters) rather than using JavaBean definitions. The current concept has been outgrown now that we support @Comment on the field—it's awkward that @ExportName needs to be set on a method, not to mention that @Transient is hard to "find out" about.

Note: This is probably a prerequisite for #135.

To do:

• Change @ExportName to go on fields
• Based on field names and methods, infer what properties a class has
• Introduce dedicated @Ignore annotation to ignore properties? Might be useful later on if we have "value classes" -> #12

Open point: For #135, we might have to infer the properties not by field but maybe by a method or constructor that is annotated somehow... So a bean property class probably can't have a "setValue" anymore? ...