[IMP] l10n_pl: some corrections in Polish CoA

PLN as default currency
Many improvements in taxes and fiscal positions
Fixes #825
[ADD] web_pdf_viewer: PDF in-browser preview

This module extends web client and reporting tool in order to allow a
preview of PDF files directly in the browser (if supported by the
browser). If you disable it, standard file download stays available.
[FIX] google_calendar: browse user as SUPERUSER_ID to be able to write/update google_calendar info on user
[FIX] web_tip: scroll if needed prior to displaying a tip
[IMP] sale,purchase: allow invoicing

(closes #500)

(cherry picked from commit 84c0595aef3a417702c81b5226ae1f61817a2bf8)
[FIX] sale: move menu to avoid error at install of website_quote

(closes #2728)
(cherry picked from commit 2b1e1e70dd537f02f776e58c9def195ecff839c5)
[ADD] website slides module
[FIX] broken view xml
[REF]: refactor clides to adapt channel concept

[IMP]: implement like button

[IMP]: add like button on slide detail view

[IMP]: different aspect ratio for slide and video

[IMP]: improve channel landine page
[IMP] imporve like/dislike feature on slideview
[IMP]: implement channel gridview
[IMP] small layout improvement
[IMP]: improve subscrive view on channel page

[IMP]: small improvement, added back button beside titles
[IMP]: small improvements based on the review
[FIX]: small fix for creating slide
[FIX]: small improvements based on the review

[IMP]: implement channel promote method for channel

[IMP]: fix based on the review

[IMP]: implement channel notification for new slide published

[FIX] fix view for types and sorting

[FIX]: fix filters and sorting

[FIX]: fix filters and sorting

[FIX]: fix filters and sorting

[FIX]: fix filters and sorting

[FIX]: small fix

[FIX]: fix filters and sorting
[FIX] like/dislike + invalid url redirect
[imp] website_slides: implimented pdfview
[FIX/IMP] Add slide dialog box should display progress when fetching data + fix page title of detail slide view
[IMP]: implement url based on the content types and tags

[IMP]: implement url based on the content types and tags

[IMP]: implement url based on the content types and tags

[FIX]: small for broken url when adding new slides

[IMP]: small fix for url based on the content types and tags

[FIX]: change icon for the pdf viewer

[FIX]: fix url when sending in email

[FIX]: small view fix

[FIX]: small view fix

[FIX]: small view fix

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review
[imp] website_slides: optimized performance of pdf viwer
[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review

[FIX]: fix some small issues based on review
[IMP] [website_slides] fatched youtube thumbnail image and video description