webui: Only display file/swift options when relevant backend is used
webui: Improve strings
Merge pull request #123 from dirkmueller/release/pebbles/master

Allow to select rabbit as notifier_strategy
Merge pull request #125 from vuntz/improve-webui

webui: Only display file/swift options when relevant backend is used
use xxlarge for File paths

Those tend to be very large.