Redesign import metada panel with extjs ui components

Get new import metadata window from other action menus like the new metadata creation window.
Same behavior as old ui admin metadata insert page :

![gn-insertmd2](https://f.cloud.github.com/assets/1491924/862555/07f0b636-f5f5-11e2-82fe-8653eeb34cba.png)

![gn-insertmd1](https://f.cloud.github.com/assets/1491924/862554/05fafe9a-f5f5-11e2-87a5-6a1d077594a2.png)


Thanks to Ifremer.