Some changes on "Import news from RSS" screens.

#3455


* Rearrange fields and add descriptions on "Add feed importer" screen.

* Add "View" link next to the text "Imported" on "Import news from feed item" screen.

* Fix redirection after adding importer.



Screenshot from a VSite:
![reader_2](https://f.cloud.github.com/assets/3273122/993170/a5dcf84e-0993-11e3-94cd-7e80ef900417.png)





Screenshot outside of VSite:
![reader_1](https://f.cloud.github.com/assets/3273122/993168/a2c1cd74-0993-11e3-83d2-f87b4ac73fce.png)