Odoo Release Updates

[IMP] website: apply CachedModel to website

[FIX] website: fix hoot test case for overlay buttons

[IMP] html_builder, *: rename resource and class

[FIX] website: allow customizing style of several mega menu

[IMP] website, *: document Plugins shared methods and resources

[REM] website, *_editor: remove youku platform support in media dialog

[FIX] website: move discuss bubbles while editing

[FIX] website: keep form field disabled when needed

[MOV] html_builder, website: move generic save_snippet

[FIX] website: prevent traceback when clicking on Bento block

[FIX] website,ir_http.py: slug normalized to NFC

[FIX] *: replace `btn-default` for `btn-secondary`

[IMP] html_builder, *: rename the o_editable class by o_savable

[FIX] core: fix uninstallation for model extension

[IMP] website: empty default value for selection field in form builder

[IMP] html_builder, web, website: document services and registries

[FIX] website: Make menu inherit header font-size

[IMP] website: bind s_blockquote options on parent handler

[REF] mail, *: replace core/common/record imports by model/export

[FIX] website_slides: adapt fullscreen highlighting interaction

[IMP] website: link state field to country field in form builder

[IMP] html_builder, *: improve multi layer background support

[FIX] website, *: checkered background display in the color presets

[FIX] website: add versioning for GallerySlider interaction

[IMP] website*: remove useless invisible fields

[FIX] website: keep font plugin in translate mode

[IMP] website: add an outline option for gallery miniatures

[FIX] website: fix bg color selector

[IMP] website, website_payment: re-use real snippets in tests

[FIX] website: process snippets & avoid inlined snippet with test helper