To migrate, run:
alter table stock add column payment_request_uid bigint unsigned after funding_uid, add index payment_request_uid (payment_request_uid);
alter table inventory_stock add column payment_request_uid bigint unsigned after funding_uid;

To migrate, run:
alter table stock add column funding_uid bigint unsigned after payment_uid, add index funding_uid (funding_uid);
alter table inventory_stock add column funding_uid bigint unsigned after payment_uid;

This hurts performances a lot.

... instead of relying on automatic migration.

This fixes TestCMFActivity.test_connection_sortkey on Zope 2.13

Use already existing system preference and created accessor rather than hard coded value which was different from
default for the system preference
This can lead to different cache ids generated for same content by different
parts of the code -> duplication of same data in cache backend.

When a ZODB connection is closed, it usually returns to a ZODB pool and may be
reused by another thread. If the SQL connection was open and is still in ZODB
cache, the _v_database_connection attribute is still there:
ActivityConnection.connect() is not called and a new instance of ZMySQLDA.db.DB
is created for the new thread without initializing its sort key.

Here the list of changes:
- close all timers when quitting, this makes stopping an erp5tetsnode
  much faster
- remove hack on slapos/testnode after fix of slapos.cookbook
- remove old tmp files left by buildout (buildout has te bo fixed too)
- remove logging handlers where the are not needed any more
- fixed the kill command, it was not able to kill properly childs

see 182eb94a in slapos repository.

see 182eb94af4 in slapos repository.

This speeds up a bit, but not having to keep synchronized a connection that is
never used.

accept checked_permission parameter in explicit definition of getQuantityUnit() because checked_permissin='View' can be added in ERP5Form.Form.DefaultValue.__call__.