[FIX] fetchmail: do not delete a failing email when using POP

In case of IMAP, the email is simply set as read but in case of POP, the email is deleted. To avoid loosing data (e.g. misconfiguration of server), the email is kept for POP.
Bug lp:1296724, opw 605667
[FIX] point_of_sale: generate bank statement with commerical partner

When a pos session is closed & confirmed, the account.move were generated with the commercial partner except for the bank statement which prevented automatic reconciliation.
This patch uses the commercial partner also for bank statement.
Fixes #1558, #1764
[FIX] board: Do not offer to create dashboard when there is no action

In case we have no defined action (e.g. redirection by python code), adding a dashboard should not be possible as the rendering based on the action.
This patch hides the 'Add to Dashboard' button in search view (opw 611288)
[FIX] hr_holidays: employees cannot approve their holidays

Nor modify once approved

It wasn't possible for employees to approve their holidays themself, thanks to the GUI, but this was possible through xmlrpc calls, or when altering the html directly in the browser.
Besides, this was also possible to edit the holiday through the same trick once the holiday validated
[FIX] product_visible_discount: use order date to compute currency instead of current date
[FIX] sale_order_line: use order date to compute currency instead of current date
[FIX] security: ir.config_parameter should not be readable by externals
[FIX] security: externals should be able to read attachements

without having the rights to read ir.config_parameter
[FIX] security: res.groups should be readable by admins only
[FIX] security: remove read access on company critical fields
[FIX] security: disallow read on ir.sequence for externals
[FIX] email_template: security, email_template no rights for externals
[FIX] resource: security, resource not readable by externals
[FIX] account: avoid date and cache issues

Explicitely refresh invoice browse_record(...) in order to have correct 'date' in account.move.
Use context_today() date instead of time.strftime() for date_invoice. (opw 611210)
[IMP] report_sxw: missing parameter without_company for display_address

Fixes #811
[MERGE] forward port of branch 7.0 up to 3509e15
[FIX] hr_holidays: remove now invalid xml attribute "model" (introduced by last forward-port)
[FIX] account: use method has_group() instead of browsing the group directly.
[FIX] base: security: employee must have access to res.groups
[MERGE] forward port of branch 7.0 up to f65c913