Feature (Snapshots/Repositories) : added screen for repository creation and deletion

Feature (Snapshots/Repositories) : added screen for repository creation and deletion

Added screen to manage add/delete of repositories. 
This is the first step to complete snapshot/repo CRUD. 

Please review menu icon (briefcase? and let me know if you want something different). 
Please review code and provide feedback. 

Next Steps:
- add individual snapshot control per repo (second set of create/table controls on screen, with filter by repo?)
- dropdown for type instead of free form (I think fs is the only for now but s3 and hdfs is coming soon) 
- unit tests?

[ES 1.0.0 Doco for Repositories/Snapshots](http://www.elasticsearch.org/guide/en/elasticsearch/reference/master/modules-snapshots.html)