[FIX] missing multi company currency access rules, set currency.company_id to False by default
[FIX] remove company_id from currencies in currency_data.xml
[FIX]ir_sequence: fix cryptic error message when prefix/suffix is not in a valid format and update number_next in order for it to have same value as the sql sequence preventing the sql sequence to restart from one if a write is done.
[MERGE] res.currency: default to global currencies in multi-company setup + add proper ir.rule, courtesy of Alexandre Fayolle (Camptocamp)
[FIX]ir_sequence: only execute a change on postgresql sequence when really needed and add a field to get an approximation of the current next_number.
[FIX] modify domain evaluation tests to avoid relying on res.currency entries assigned to companies, as demo data was modified for bug 1111298
[FIX]ir_sequence: better args definition
[MERGE] res.currency: default to global currencies in multi-company setup + add proper ir.rule, courtesy of Alexandre Fayolle (Camptocamp)
[MERGE] ir.sequence: lazily compute next value for PostgreSQL-backed ir.sequences + avoid resetting it at each change to the sequence, courtesy of Ronald Portier (Therp)

The original patch proposed by Ronald has been modified to
make it more suitable to a stable version, in the following
aspects:
- remove all extra physical columns (boolean flags), as they
  would break the stable policy and were actually unnecessary
  to fix the bug
- avoid displaying both the number_next and the number_next_actual,
  the latter is sufficient
- fix a possible bug when setting the number_next to 0
[FIX] ir.sequence: add a proper default value for number_next_actual (0 is disallowed by default) + avoid error when trying to alter a sequence during creation