For backward compatibility with ingestion policy scripts, the message body is
turned into a 'data_chunk' request parameter.

By not having anymore to convert to/from application/x-www-form-urlencoded,
this fixes a severe performance issue, in particular when ingesting a lot of
data with fluentd (Ruby uses regex to convert).

/reviewed-on !28

/reviewed-on !25

Not always we have ZBIgArray set to an ERP5 Data Array thus handle this case and return None if missing.

Related bug report: https://nexedi.erp5.net/bug_module/20160711-1D0657A.

/reviewed-on nexedi/wendelin!21

@Tyagov @kirr Configuration is currently done through python script, this could be improved. In current design, if messages cannot be forwarded as fast as new messages come in, some messages will be skipped.

/reviewed-on !22

While investigating fixes to https://nexedi.erp5.net/bug_module/20151207-1789A61 I found that it was impossible to reproduce this bug in Wendelin tests due to a bad configuration of how WendelinInformationGadget was installed.  Now I can Wendelin tests (still get a different problem though, which is subject for another PR or bug report).

Please review, @Tyagov.

/reviewed-on !20

/reviewed-on !19

So that it can be selected as "Product or Service" in Data Analysis Line

And also allows the user to choose to not install it.

A proper warning with regards to remote code execution is displayed,
even though it could only happen if the "attacker" has valid ERP5
credentials.

@Tyagov, please review.

/reviewed-on nexedi/wendelin!18

@Tyagov all templates from the Wendelin repository migrated to new format using Portal Template's import/export tool. 

/reviewed-on nexedi/wendelin!17

@Tyagov this fixed the test suite error, sorry. 

/reviewed-on nexedi/wendelin!16

@Tyagov, can you merge, please? 

/reviewed-on nexedi/wendelin!15

```
1. portal_gadgets/WendelinInformationGadget state should be made public (not invisible like now)

2. portal_gadgets/WendelinInformationGadget should have a default thumbnail (i.e. image). You can simply make print screen and add it

3. When Wendelin gadget rendered I see links like http://wendelin:2200/erp5/$%7Bportal_url%7D/portal_skins/erp5_data_notebook/manage_main looks like script not called that replaces it dynamically ?

4. In /DataStream_view my_append_file is in group "not_assigned" but it should be right under "my_file" in "right" groupd
```

@Tyagov: everything fixed as requested.

/reviewed-on nexedi/wendelin!14

The gadget now has the published state and content variables are working through
using .getStrippedHTML instead of .getData to render the web page.

/reviewed-on nexedi/wendelin!13

The Append File control is hidden when the Data Stream is empty and enabled
when the Data Stream already has content. Meaninful notes were added to both
Upload File and Append File control to avoid confusion.