ERP5Type: introduces 'type_definition', a grouping type to identify portal types defining other types

ie: Base Type and portal types of portal types

erp5_accounting,erp5_project,erp5_payroll: changes type of main Accounting and Task documents to Delivery type

For the moment it only allows to define a list of ledgers
on the portal types inheriting from it, to create a filtered
list of ledgers allowed on the final objects.

It allows to set up the default ledger on these documents too

New accounting documents belong to some "ledger/accounting/X" category
  if such is defined in the accounting preferences.
Accounting views of some documents now include a ledger.
_viewAccountingTransactionList forms can filter on preferred ledgers.

Which was related to an older version of the simulation

For example, Python Scripts were:
- dirty in the imported BT (causing all of them to be reinstalled on upgrade)
- compiled to return None

When a currency exchange line is (in)validated, we need to reindex the currency exchange
cells that acquire validation state from the currency exchange line.

This allows defining an exchange rate without end date

https://codemirror.net/demo/activeline.html

since be31425e

not only complete python language words but also all words from the
buffer.

/reviewed-on nexedi/erp5!122

Mark the test as expected failure for now.

This test is in expectedFailure state and is still not passing with this
change, but this test was showing wrong example that can cause
confusion.

Here are 2 examples of fixed cases:

- File object with data=None was exported with a second file containing the
  string 'None'

- Zope Pages Templates (and derived OOoTemplate) relied __setstate__ to fix
  the wrongly imported object.

This avoids computing a file extension that may not be used (if there's no data
to export), and fixes unreliable code duplication in _guessFilename().

Plus more implicit acquisition fixed.

We'll add another test checking that nothing is exported as a separate file.