[FIX] data dir when home is not a directory

Use site data dir instead of user data dir when user's home is not a directory.
Like system users created with /dev/null as home.

Stricter than before.
[IMP] website.snippet: create automatically the thumbnail; data-option became data-js; add data-eval method; rename check_class into toggle_class
[FIX] website.snippet: the background option is not readily usable by the designer
Merge pull request #2050 from odoo-dev/master-theme-review-chm

[IMP] website.snippet: create automatically the thumbnail; fix background
[IMP] qweb debug mode restricted to --dev mode

Also moved the set_trace call in top of render_node() function so it
makes more sense.
[IMP] Make translation todo's readable when hovered
[IMP] stock: allow float precision for quantity qty multiple

e.g. if orders with packages of 1/2 quantity
Merge pull request #1343 from vice/master

[FIX] data dir when home is not a directory
[IMP] [DATA] product: added default product.product data (Miscellaneous), consumable and available for the point of sale.
[UPG] web: upgraded font-axesome to version 4.2. New icons! Shiny! Lots of fun!
[IMP] sale, website_quote: expiration date is usefull even without using the website_quote module, therefore movign the field to the sale module. It has also be added to the email templates defined in sale and portal_sale, as well as in reports.
[IMP] crm, sale_crm: onboarding-related fixes
- lead name is now called Opportunity, clearer, added a placeholder on the form view;
- type (contact type) field is now dedicated to the group_delivery_invoice_address group.
It is set for technical groups only in base, then upgraded to the correct group in the
sale module that defines this group
[IMP] sale_crm: on opportunity form view, add a button linking to the
sales related to the current opportunity, using a stat button. Two fields are
introduced: opportunity_id on sale.order (automatically set when using the
make sale wizard), and sale_amount_total on the opportunity, function field
computing the total amount for the not canceled quotations related to the
opportunity.
[IMP] share: now restricted to the technical group, as this is a very
tricky feature. Also changed the order in the more menu.
[IMP] account, account_bank_statement_import: onboarding tips. Added 2 data files holding 2 tips for account, 1 for account_bank_statement_import.
[IMP] website: image controller can use xmlid
Merge pull request #2153 from odoo-dev/master-website-image-controller-chm

[IMP] website: image controller can use xmlid
[IMP] mail: chatter: Send message / Log a note tooltips improvements, to better explain to the user why the world is about to collapse into a molecular singularity.
[FIX] web_tip: don't display tip on element whose width or height is 0

This commit allows a tip to be properly displayed on elements containing
an img tag. Previously the tip would be displayed before the image could
be loaded, thus breaking the ui.
[REM] website_blog : Remove all things related to blog.post.history model