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__.

Refactor code to remove code duplicated related to get real context. Also, the language is removed if exists and the context is a Web Section or Web Site

Fix bug on budget consumption views, sum and details where using different simulation state parameters
Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

* Base_getPreferredPrecision: there are no such thing as a global preferred
  precision. We should use the precision of the resource or price currency
  depending on whether we display quantities or prices.
* Base_getRoundValue: just call round or use precision= parameter from
  inventory API

Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

The month was taken from a date in the wrong timezone
Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

http://erp5.nexedi.com/bug_module/1591

And replace is uses by AccountingTransactionLine_getNodeItemList