Create Annotation for constructor parameter names and ParameterNameDiscoverer to understand it

See http://shibboleth.net/pipermail/dev/2016-September/008570.html

This is a cross project work item, starting in Java-support with an implementation in Spring-extensions and then a scattering of annotations across the entire stack.

The problem is that given

we have made 'paramtre' part of the external API, becaause someone might have said c:paramtre="foo" in a bean file.

If someone comes along and fixes the spelling thjen the bean file will stop working.

The idea is to add an annotation (so that we know not to change it), but the geneous bit (thanks ) is that if we implement a org.springframework.core.ParameterNameDiscoverer and inject it suitably we can automate the process, so ion the above example it would be

class wibble {
public wibble(@ParameterName(name="parameter" Object renamed) {...}
}

The parameter name is removed from the public contract (whilst the ParameterName becomes part of it).

If this class inherited correctly we should be able to fall through into the default behavior - it would be nice to warn if we did do this for one of our classes.

Of course the problem then becomes of what to annotate, I think we need to annotate every constructor with parameters in the api trees of the IdP. OpenSAML is harder since (AIUI) the api-impl split isn't nearly as clean. I'll be asking for Brent's help there.