This allows to set all kinds of arrow properties while keeping the main view simple.

The previous implementation did not support saving categories in view form.
It is better to use standard Base_edit in view forms and put actions which are other than "save"
into a dialog.

getArrayDtype can be used for example by html5 app to display graph with correct dtype

data model: split ingestion policy script (tag parsing) form ingestion operation (writing to data stream)

Interaction workflow could still be used to call the alarm right after appending to data stream

@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 nexedi/wendelin!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 nexedi/wendelin!20

/reviewed-on nexedi/wendelin!19