* Fix lookup of the BT with the highest revision (getRevision method does not
  return an integer).
* Automatically build a non-built BT before exporting it.
* Make template tool export BT like a classic HTTP file server.
* Unit tests: allow to specify in --bt5_path any HTTP url. Existence of a BT is
  done by a HEAD request to avoid downloading twice.

So now, the URL to specify in --bt5_path must be of the following form:
  http://.../erp5/portal_templates/asRepository
It could also be http://www.erp5.org/dists/snapshot/bt5/

A normal ERP5 instance can also import a BT from another instance:
  http://.../erp5/portal_templates/asRepository/erp5_base

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@33414 20353a03-c40f-0410-a6d1-a30d3c3de9de