Tweak social/sharing icons

[alanorth]

In #150 I added a few common social icons for sharing, but we need to add Delicious and Mendeley if possible. Also, we need to make the sharing links open in a new window, and perhaps get the title so share in the tweet intent (will have to do the math and truncate to tweet size).

[alanorth]

Someone created Academicons, which has Mendeley and Google Scholar:

https://jpswalsh.github.io/academicons/

[alanorth]

Instructions for using Mendeley sharing URL here:

https://www.mendeley.com/import/information-for-publishers/

[alanorth]

Mendeley icon and sharing works:

Code in https://github.com/alanorth/DSpace/tree/5_x-sharing-icons. Still need to do Delicious, and set the links to open in new windows.

[alanorth]

Might as well update FontAwesome here too.