Prior to this change, license.txt and notice.txt files were duplicated
across every subproject in their respective src/main/resources/META-INF
directories.
This commit centralizes these files under the root project at src/dist,
along with the changelog and readme files. The definition of the 'jar'
task has been been extended to include the license and notice files in
module jars as they are created.
The directory is named src/dist because these files are all related to
distribution - the readme is different than the one you see at the root
of the source tree - the intended audience is for users who download
the spring-framework distribution zip. A task to create that
distribution zip will be added in subsequent commits.
