erp5_email_reader: use transaction cache instead of read-only transaction cache
doc: fix typo in simulation diagram
Bug Line: remove file after clone
Test: Repair --run_only

Amend 9240d49802534b7b13902e0d211b606cf1450426: Since many Loaders are
instanciated by unittest itself, filter_test_list still have to be a class
variable
Test displaying and validating a listbox with other field on the page
Listbox: Cleanup REQUEST.cell ( same as 6a83d60 )
ZSQLCatalog.zsqlbrain: Avoid traversing on each getObject call.
ERP5Type.Base: Trivial cleanups for getCreationDate.

- do not use getToolByName.
- do not put two statements on the same line
- merge nested "if" statements around a single code block