[FIX] web: fix view manager header height form view

in form view, the header height was higher than in other views (4 extra
pixels). This was caused by the floating buttons in
.oe-view-manager-buttons.  This commit forces the column to take exactly
30 px regardless of its content. (it is not a problem even if the
content takes extra lines)
[FIX] mail_tip: prevent blank webclient
[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] Uniformize the icon in all kanban view (Google Hamburger)
[REM] CRM : Remove old php script from crm.
[IMP] website: replace ckeditor by summernote
[FIX] website editor
[FIX] website: auto-increment when new page; fix link (key) search page