Specify ComponentConfigurator hint in Mojo doclet tags

This patch adds a @configurator <role-hint> tag to the
JavaMojoDescriptorExtractor so Mojo implementors
may override the default 'java' ComponentConfigurator.

This makes it possible to handle parameters in mojo specific
manners, should there be such a need.

(The patch doesn't affect existing mojo's, it just exposes
the role-hint which is left to a default (not set) in the Java
extractor and set to 'bsh' e.a. in the other Extractors).