New import ui dialog

This work is to move the import ui from the bottom-left to a centered dialog window.
![testvcard1](https://cloud.githubusercontent.com/assets/3966617/2911446/510f3ea8-d65c-11e3-89e8-c461ac3210e7.png)
Few problems remain, like the upload button which can't be easily moved to a specific location probably due to css rules.

Next step in the todo list will be to let choose the input format with the calculated probabilities if the user selects `Automatic format` in the format list.
![1362f9e2-c65c-11e3-8a02-bdc073c1998a](https://cloud.githubusercontent.com/assets/3966617/2911480/bc6c6f9e-d65d-11e3-9468-e9cce0623681.png)