(maint) Ignore ext/packaging

This commit adds ext/packaging to the .gitignore for puppetdb and also excludes
it during tarball creation in the tar rake task.
(maint) Copy filesystem utility methods from packaging tasks

As the install task uses cp_p, cp_pr and ln_sfT, this commit copies them back
into the top level Rakefile for use during build, as the external packaging
tasks will not be available at that time.
Merge pull request #447 from haus/fix_package_building

Fix package building