[FIX] product: make sure unlinked product still exists

When uninstalling/updating a module, we may execute unlink method on product.template before product.product. In such cases, the product is already removed after removeing the template (_inherits) and the chained unlink of the product would fail (traceback when browsing).
[FIX] point_of_sale: the product name field changed to display_name to include variants information, this should be reflected in searches as well.
[FIX] website_customer: the extra / for url pager is not need in saas-4
[FIX] point_of_sale: the order uid were generated via timestamp, which were not sequencial or easy to understand, they are now generated with the order id and order sequence number which are sequencial
[FIX] website_twitter: IE does not accept twitter date format

Datetime like Tue Jul 13 23:18:36 +0000 2010 is not accepted by IE and return "Invalid date".
Therefore, We parse the date to a format known by IE (and other browsers)
Trick took from http://stackoverflow.com/questions/3243546/problem-with-javascript-date-function-in-ie-7-returns-nan
[FIX] point_of_sale: invoicing in the pos printed the wrong order due to a mismatch between order ids and invoice ids
[FIX] account_analytic_analysis: quantity overdue on quantity exceeded, not reached
[IMP] hr: first employee is named after admin
[IMP] models: improve code of _convert_to_write(), make it easier to read
[FIX] product, point_of_sale: add a display_default_code context option that can remove the internal reference (default code) from the displayed product name. Used in the point of sale to unclutter the receipt & GUI
[FIX] mrp_operations: use list instead of record set for o2m

In v7, accessing a o2m returned a list of browse record while it returns a recordset in v8.
The method _move_pass expects a list so a manual conversion is required.
Fixes #1787
[IMP] bundles: also display css errors on debug mode
[FIX] website_forum_doc: fixed tree view impossible to use to create new chapters (missing forum_id due to wrongly copy-pasted views) + fixed max width of images displayed in the doc.
Merge branch '8.0' of github.com:odoo/odoo into 8.0
[FIX] point_of_sale: copy/paste error, super must use the apropriate class
[FIX] account_voucher: avoid error if no partner

The field partner_id is not required on an account.voucher but the validation was failing if none was set (opw 611663).
This patch makes a fallback on the account of the voucher if neither a partner nor a writeoff account is specified.
[IMP] account_voucher: make the field tax_amount always readonly

The field tax_amount is fieled with onchanges and the compute_tax method. Setting a different value than the one computed by the system may lead to unbalanced move (which is obviously wrong).
In the future, handeling these operations by setting the correct value to the tax accounts would be better.
[IMP] Cache bundles in ir.attachments instead of LRU
[IMP] website_quote: handle quote and website descriptions

Add field quote_description on product.template and turn website_description from sale.quote.line into a related.
Overwrite write and create methods to synchronise both fields when setting a product.
website_description on product.template is added by website_sale but there is no dependency relations between these modules so we need to define it in both modules.
[FIX] sale: define sale_note field before using it as a default value for sale.order

When uninstalling/installing sale module, this can be problematic