provide parent project.clj file

[loomis]

Provide a parent project.clj file for managing dependencies and repositories in leiningen builds.

[loomis]

In the PR, there is an implementation of a parent project.clj file that can be built from maven, along with the rest of the build. Here are the caveats with this addition:

• The build uses the maven-exec-plugin to call lein with appropriate arguments. Nothing fancy here.
• The build is conditional on /usr/local/bin/lein existing on the build machine.
• The version number must currently be updated by hand with releases.
• This correct lein path is NOT available on Jenkins currently to avoid failures in the build related to updating the project.clj version numbers in a release.

• The extra subdirectory lein-parent/parent is required to avoid having lein overwrite the pom.xml file when running an install.

  The entire project.clj file is a work in progress; comments on the organization and content are welcome. In particular, the repository configuration needs work.