templates: UI design enhancements and tweaks

* changed the layout of news feed
* designed the buckets according to the mockups
* cleaner design for navbar
* updated logo

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
templates: design enhancements and fixes

* added signin options with arxiv and orcid
* added content in People bucket
* style buttons for Literature
* UI improvements

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
templates: small adjustments to front page

* Updates tags of most viewed/cited
* Change in text to "Connect your ORCID"
* Update glyphicon in People bucket

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>