doc directory and multi-module projects

[Tom Zeller]

>>If your multi-module project has just one
>>packaged output then maybe you can put the release notes in the module
>>that creates that.

Maybe documentation for IdPv3 should be in
idp-distribution/src/main/resources, in a new doc/ directory. Either
the idp-distribution pom or assembly descriptor could aggregate
documentation from child or peer modules.

>>  That feels a bit weird, though: for the MDA, for
>>example, at the moment the only packaged output (packaged other than as
>>individual .jars, I mean) is the CLI module and that doesn't feel like
>>the right place to put release notes to me, particularly if another
>>module might one day package a .war for a web application.

The MDA might need its own "distribution".

> Maybe we need a doc submodule.

Something like idp-doc, sure.