TAJO-1244: tajo.worker.tmpdir.locations should use a validator for a list of Path.

Closes #298
TAJO-1243: *-site.xml.template should have default configs commented out.

Closes #297
Change documentaiton url of devel and current versions.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-1241