The ArtifactDeployer isn't the prefered choice and there's
no reason to make BASE_PATH handling more confusing than necessary,
so just drop the userContent magic.
If we switch the directory we might end up in the wrong directory
for further actions, so run all the commands around svn-buildpackage
in a subshell.
Also replace the --svn-move command with --svn-move-to to place
the artifact files in the original directory, otherwise the files
might be placed in the wrong directory if $branch is set and used.
For the timestamp we're now using seconds since 1970 (date +%s).
This will always increase over time whereas svn revisions might
not be consistent over all the time and building on slaves might
cause lower build numbers.
So lets use ...~${TIMESTAMP}.svn${SVN_REVISION}.${BUILD_NUMBER}"
as the version schema to get increasing version numbers no matter
what.