add Syncronize>Remote deleted branchs to local

[gganster]

Hi,

I think this use case can be usefull to add

use case: when a branch is deleted on remote (from github.com for example), this deletion isn't syncronized automatically in local.
This can be done with git fetch --prune.

I can contribute. Just need feature validation for start.

Good job for this tool ;-) I think i will use it for teaching to juniors in my startup.