[RAT] Changes plugin

[sebb <se...@gmail.com>]

I have updated RAT so that the changes plugin can be used to generate
the release notes.

The command to do this is:

mvn changes:announcement-generate -Prelease-notes [-Dchanges.version=0.11]

(this is documented in changs.xml).

The changes plugin only supports generating output from a single
version, so if we want to keep historic release notes, we have two
choices:

1) maintain a separate historical release notes file and copy the data
across on a new release

2) add the historical data to the changes/release-notes.vm file

Otherwise we can do as Commons do which is to generate release notes
for the current release only, and have the historical releases as the
Changes report on the website, for example:

http://commons.apache.org/proper/commons-net/changes-report.html

I have started copying the data from R_N.txt into changes.xml.

S.