See merge request nexedi/slapos.core!222

See merge request nexedi/slapos.core!240

This reverts commit 7e49ec5e.

This reverts commit febcf1b4.

See merge request !239

See merge request nexedi/slapos.core!185

See merge request !236

We observe that software sometimes fail due to transiant errors such as
DNS/network errors, so increase the default number of retries to build
software from 2 to 10.

Sometimes also instance is failing for monitoring or other errors that
might become OK if we retry more, so increase the default number of
retries for instance from 10 to 20.

  It was added as "0" in order to run first, as the later tests calls logout and can be started as anonymous.

Files on the partition can be created with mode disallowing removal, so use
slapos.util.rmtree to ensure they will get removed instead of failing.

In some cases partitions can chmod -w some paths, so use util.rmtree to
overcome this situation.

   ... rather them the user's language

   Payment mode is set on the payment object and invoice

    Also inform payment_mode to let the script handle the display of information

  * erp5_immobilisation is now installed
  * "Update translation table" is verbosed as some bt5 are always marked to be resinstalled

    Use Wechat payment rather them payzen

Also change places where xml_marshaller were used directly to always use
the wrapper from utils (except in tests for simplicity)