point_of_sale: Add _prepare_analytic_account method to easily set analytic account from custom module
[IMP] doc: remove guides section, move themes to tutorials and rest to reference

also pass PNGs through crusher, turns out dot produces pretty terrible PNGs
[FIX] base_iban: IBAN constraint trigger

Make sure the constraint on IBAN format is checked when either the state or the account number is changed.
'iban' field was not modified so the check never triggered and could enter invalid IBAN
Fixes #3426
[FIX] web: t-attf expects #{} or {{}} for variables

not just {}. Nevertheless, It somehow worked in Odoo 7.0 and saas-3.
[FIX] website: main layout - title more flexible for customization. (additionnal_)title was overwritted by website_meta_title or main_object.name
Merge pull request #3332 from akretion/8.0-prepare-analytic-pos

point_of_sale: Add _prepare_analytic_account method
[IMP] use model._fields instead of model._all_columns to cover all fields

The old-api model._all_columns contains information about model._columns and
inherited columns.  This dictionary is missing new-api computed non-stored
fields, and the new field objects provide a more readable api...

This commit contains the following changes:

 - adapt several methods of BaseModel to use fields instead of columns and
   _all_columns

 - copy all semantic-free attributes of related fields from their source

 - add attribute 'group_operator' on integer and float fields

 - base, base_action_rule, crm, edi, hr, mail, mass_mailing, pad,
   payment_acquirer, share, website, website_crm, website_mail: simply use
   _fields instead of _all_columns

 - base, decimal_precision, website: adapt qweb rendering methods to use fields
   instead of columns