UI: Remove "Lorem ipsum" below images on Edu/Rsrch

* (closes #298)
UI: Replace image for "histograms"

* (closes #299)
UI: introduces "Export" modal/popup

* (addresses #303 , #304)
collection: lighter black on "more" button

* (addresses #293)
UI: FIX OL broken on "physics" page

* (closes #309)
data: addition of CMS masterclass files from DocDB

* Adds CMS masterclass files from DocDB.  (closes #67) (PR #287)

* Merge note: installation instructions amended accordingly.

Tested-by: Tibor Simko <tibor.simko@cern.ch>
docs: addition of issue stats and licence badges

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
docs: fix for licence badge style and link

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
UI: changes logo back to HTML/CSS
UI: responsiveness on "Homepage"

* (closes #76)
UI: introduces experiment images next to actions
UI: introduces breadcrumbs in pages

* (addresses #316)
UI: testimonials styling
UI: removes background colour from entrypoints
menu: adds "education","research" - rearrange
resources: added external link btn + minor styling
UI: fixes bullets for lists

* (closes #315)
logo: new svg outlined "opendata" logo

* fixes cross-browser problems (closes #310)
UI: fixes link to CC0 and CC0 image

* (closes #139)
collections: fixes filesystem conflict OSX/SLinux

* fixes issue with capital letters in filenames on SLinux systems