Dialog to set start and end records for export

In response to #2449, I've created a modal dialog for setting start and end records when exporting using download links.

The PR also modifies apply_pagination so that it respects `export[:start]` and `export[:end]` parameters.

![screenshot from 2013-10-27 22 24 16](https://f.cloud.github.com/assets/1596233/1416562/2fb78b4c-3f59-11e3-9e21-f7b3d11bd1c4.png)

Related: #1924