use svg icons in browser dock for uI consistency


this commit creates a new svg Add icon (based on other Add Layer icons) and uses that icon as well as the new SVG refresh icon, which makes UI more consistent

before: 
![browser1](https://f.cloud.github.com/assets/1018556/1082204/c69e0166-1584-11e3-9320-d0a7a4112276.jpg)

after:
![browser2](https://f.cloud.github.com/assets/1018556/1082209/ccfb41b8-1584-11e3-8835-fbd4c3c79cf9.jpg)

and using the Expression filter icon, which doees not look good (not included in this pull request)
![browser3](https://f.cloud.github.com/assets/1018556/1082219/dcee9444-1584-11e3-99e2-693089a61ab2.jpg)