This caused two problems:
 - If Xfvb was killed and left a stale lock file, we don't reuse this
   display. After some time we end up having "All display locked"
   exception but no Xvfb process running.
 - Xvfb's slapos is patched to store control sockets and lockfiles in
   $TMPDIR ( slapos@58462c24 ).
   We don't have $TMPDIR set in testnodes, but this would be a problem
   if we ever set it.

Because Xvfb can detect a stale lock file upon startup and start anyway,
the easy way running Xvfb for each display and see if it's still running
after a few seconds.

@Tyagov 
 
Added a test to check int64 and float64 Numpy arrays because an error like this existed before:

```
in Base_executeJupyter
     return json.dumps(result)
   Module json, line 244, in dumps
     return _default_encoder.encode(obj)
   Module json.encoder, line 207, in encode
     chunks = self.iterencode(o, _one_shot=True)
   Module json.encoder, line 270, in iterencode
     return _iterencode(o, 0)
   Module json.encoder, line 184, in default
     raise TypeError(repr(o) + " is not JSON serializable")
TypeError: array([[ -245554.,    19410.,  1453313.],
        [ -238947.,    18888.,  1443651.],
        [ -238416.,    18350.,  1444382.],
        ...,
        [ -250816.,    19482.,  1445528.],
        [ -251464.,    18678.,  1444711.],
        [ -253475.,    18786.,  1444842.]]) is not JSON serializable
```

/reviewed-on nexedi/erp5!285

/reviewed-on nexedi/erp5!290

/reviewed-on nexedi/erp5!287

By adding returned_purchase_packing_list_builder and
purchase_packing_list_builder to Alarm_buildPackingList they are used in
tested alarms.

Returned Purchase Packing List and Returned Sale Packing List can be
generated by corresponding orders.

Test are based on testOrder logic and assertions.

By adding Returned Purchase Order and Returned Sale Order it is possible
to operate with reverse logistics: return the goods sold or purchased.

@Tyagov @luke 

See the MR at slapos [here](nexedi/slapos!177).

/reviewed-on nexedi/erp5!283

Exchange action are meant to import/export a list of documents

https://w3c.github.io/server-timing/#the-server-timing-header-field

 ... this js was already included

In its current implementation ( introduced in  4787eadd ), `variation_category` parameter of Inventory API require movements to be in the `predicate_category` table. The approach is to do a first query to get uids of all movements members of the variation and pass their `uid` to catalog. My guess is that this does not scale well. It also uses deprecated `where_expression` and generates invalid SQL when no movements match.

As far as I know, it is only used in [testInventory](https://lab.nexedi.com/nexedi/erp5/blob/ba541ad46e5c593f94fe1ebe79e99d67aafdecb1/product/ERP5/tests/testInventory.py#L1024). We could also consider dropping it, but keeping compatibility is easy.

This implementation just use `variation_text`.

[Test results](https://nexedi.erp5.net/test_result_module/20170502-1FDBAB66) are OK; there is one functional test failure but it really looks unrelated.

@yusei @vpelletier  @seb @romain do you see problems with this ?

/reviewed-on nexedi/erp5!265

Reuse code of delivery to ensure we can customize which item should be
in item table

This reverts commit 2ef67082

This allow customization, original init script is called by new script.

Performance is still not optimal, but should be better than before. At
least it does not assume that movements will be in predicate table.

- Use cloudooo instead of imagemagick
- Avoid to use (probably lossy) png format

_from_  _to_  ____id____  _______________module____________________  ______________comments_______________
pdf     bmp   pdf_to_bmp  erp5.component.document.TransformPdfToBmp  Previous: pdf-(imagemagick)->png->bmp

* acquire objectValues list method instead of using searchFolder
* acquire tales expression for selection name

this is an issue for layout of six-column grid since 16.667 * 6  > 100

/reviewed-on !279