[ADD] pad: new etherpad plugin to remove autofocus

In the form views where the pads are used, Etherpad-lite automatically
focus on the pad content, even if the user has already started to type
into another field.

This behavior is quite annoying for "quick changes", so we provide a
(very tiny) plugin for Etherpad-lite that will prevent this autofocus.

Detailed installation instructions are also included.
[IMP] account, account_analytic_analysis: fix labelling incoherences

- account: this change aims to keep the same labels on form and list views
- account_analytic_anlysis: correct search field
[IMP] website: correct page hierarchy for comparison snippet
[FIX] web_kanban: fixed issues when having no column to display in kanban
view.
[IMP] ir_ui_view: pep8 + log catched exception when view_id cannot be found.
[IMP] ir_http: don't handle exception in dev mode but use the werkzeug debugger except if cause has been already identified (website Qweb)
[IMP] remove instant click
[IMP] sale_stock: better inherit

Better inherit of tree view of sale order line with position="attributes"
instead of postion="replace"
Fixes #3664, #3726
[FIX] im_livechat : do not crash if not Referer url in the header of the request.
[IMP][website_mail] improved template designer, added support for background color, font color and bootstrap buttons(inline css) in mail designer,removed other snippet, changed snippet according to new format,added theme selector in mail_designer, lodeded snippets dynamically based on theme, added font-awesome support in mail snippets, added one controller which convert font-awesome to icon

[IMP][website_mail] changed less colorpicker to inline ckeditor color picker

[IMP][website_mail] Improved discount coupon and image text snippets