Multilingual help for JSPUI

**JIRA**: [DS-1508](https://jira.duraspace.org/browse/DS-1508)
**Documentation**: [Multilingual Help for JSPUI](https://wiki.duraspace.org/display/~joaomelo/Multilingual+Help+for+JSPUI)
**Credits**: [Lyncode](http://www.lyncode.com) + [RCAAP](http://projeto.rcaap.pt)

**NOTE**: It depends on dspace-api-lang changes.