[FIX] Solve some mail issues which are currently present in 7.0
Merge pull request #724 from odoo-dev/7.0-mail_issues-fix-adh

[FIX] mail: misc bug fixing
- avoid deleting the Whole Company mail group if still present, because it is required for some module installation. In 7.0 installing some modules may crash if this group is not present.
- fixed an issue when computing possible recipients in the Chatter
- small fix in html2plaintext about blank lines
[FIX] orm: custom m2m with different label

At rev 84e9a67cdf78db94cb7a09543c1b7ac4ad19d8b4 a check to avoid the creation of ir.model.relation for custom modules was added. The condition is not correct as based on the string instead of the field name. We do not have access to column name at this level but the the m2m relation table do start with x_ for custom fields (see __init__ method).
[FIX] hr: call hr_employee super's when unlinking

Also fixes some weird inheritance bugs in upper versions
[FIX] event_sale: reset event-related fields on SO line when switching products
[MERGE] Fwd-port 7.0 up to 783b9e1
[MERGE] Fwd-port saas-3 up to a9d2b65
[MERGE] Fwd-port saas-4 up to e31fd6a
[IMP] add read access to all users for product.pricelist.type

In new API, selection field value is checked (against the selection's possible
values) at both read and write. For pricelist.type this requires read access
to product.pricelist.type.
[ADD] demonstrate broken handling of rules access denial in new API
[FIX] only prefetch other cached records with read field uncached during _read_from_database

If expansion of the recordset is done during _prefetch_field, if one of the
prefetches (not the base record(s) but one of those selected by
BaseModel._in_cache_without) can't be read by the current user (due to an
access rule or for field reading reasons, or whatever) the whole read is
failed, even if the record which was specifically asked for could be read on
its own.

By only expanding the read set in _read_from_database, the cache is correctly
set but read() and _prefetch_field() only check the records explicitly asked
for for AccessDenied, prefetched records will only be asked if they are ever
accessed.

fixes #1013
[FIX] web_calendar: Revert d9e6a7a as was fixed differently at rev e220136

Fixing calendar view errors, opw 609989
[FIX] filtering out of records which shouldn't be fetched/prefetched

A todo would only filter out records selectioned by the same field's caching,
it should filter out on the whole prefetching selection or an other field
could/would just add it back to the set of records to fetch (and lead to Bad
Things).

Note: this probably deserves a test somehow, but I'm not quite sure how the
todos thing works so...
[FIX] base: make ir_attachment._filestore callable with kwargs
[FIX] l10n_lu: taxes (amont/aval)

The accounts "TVA en amont" were not used by the l10n_lu chart of accounts.

Instead the accounts "TVA en aval" were used for all taxes both sale and purchase taxes.

(Manual rebase of PR #735)
[FIX] l10n_lu: wrong mapping of accounts to P&L financial report

Account 655 and its child 6554 were both mapped.
Fixed by unmapping 655 and mapping all its direct children.

(Manual rebase of PR #733)
[FIX] tools: mail: fixed last commit, solving an issue with the html2plaintext introduced another issue with notes. Reverting to the first version.
[FIX] website_forum: fixed karma computation, on first vote the karma was wrongly calculated (when creating a vote, not when updating it).
[REM] cache setting in _prefetch_field
[FIX] setup Environment for the report thread