OPAL-2454: Check number of datasources before showing "Copy Data" modal.

### When selecting multiple tables with only 1 project: 

![image](https://f.cloud.github.com/assets/2565497/2337108/67bd5698-a499-11e3-8ad9-1a302388ee6a.png)

### When selecting no tables and clicking on Copy Data with only 1 project:

![image](https://f.cloud.github.com/assets/2565497/2337134/bca3649a-a499-11e3-831f-48a3b1a2dc78.png)