create_work: error out if bad ID arg in "--target_host ID" etc.

Actually we just check that the arg is nonzero.
We could look up the DB record (e.g. the host record)
but that would slow down mass job creation.
client emulator: make it work again
VBOX/WRAPPER: Introduce versioning information to the two wrappers.  It is now compiled into the executable instead of relying on file name.
WINBUILD: Minimum supported VS is now VS 2010
WINBUILD: Fix according to VS 2010 product tree changes.
MGR: Continue fixing detection of list selection and list deselection; deselecting by clicking on empty part of list control (below or on its right) does not generate any list events if the selected item has been scrolled out of view, so we must use mouse click events within the wxListCtrl.
MGR: Continue fixing detection of list selection and list deselection; It turns out that triggering on EVT_LIST_CACHE_HINT works better on Windows (native wxListCtrl) but mouse click events work better on Mac (generic wxListCtrl.)  We still need to determine which is better on Linux.
scheduler: if a result was aborted by user, don't count it as an error
file_upload_handler:
    a FCGI FUH shouldn't terminate on stop_upload, but return an error
validator:
    add '--dry_run' to validator daemon (run w/o DB update)
validator:
    added options -min_wu_id and -max_wu_id to validator
validator:
    fix one_pass: leave main loop even if we did_something
db_purge:
    keep the app_version_id in the archive
file_deleter:
    implement a 'dry_run' without updating the DB, for debugging
file_deleter:
    allow to run multiple file_deleters for the same App on different servers,
    selecting WUs by xml_doc (e.g. download_url)

    - be careful to cover all possible (xml_doc) cases in configuration
file_deleter:
- don't (try to) create directories if thes don't exist
- check return value of dir_hier_path
scheduler:
    some more debug output (version selection)
scheduler:
    some more debug output (locality scheduler)
scheduler:
    answer Bruce' question hidden in the code
scheduler:
  fix sending 'old' work in locality scheduler

  - leave locality scheduler only if there is no
  more work needed after sending 'old' work,
  in particular DON'T leave if old work for
  possibly non-locality apps couldn't be sent

  - try to send 'old' work before doing anything else