Support manually refreshing saved exports in the UI

and a few tiny ui improvements along the way.

http://manage.dimagi.com/default.asp?115489

depends on https://github.com/dimagi/couchexport/pull/97

![image](https://cloud.githubusercontent.com/assets/66555/3385763/d57135d4-fc6d-11e3-89eb-7153a353765e.png)