Auto "disable" repo, if can't connect via SSH

[alexgarbarev]

Hey Alex!

I've found a problem..

1. I've migrated my redmine installation from one server to another
2. I setup cron task on new one, to sync repos
3. I didn't import all necessary keys in proper time (so I couldn't clone all repos) .. And I've got "abuse" warning from hosting, since my IP address is trying to "attack" some server. That was because of combination of cron task and incorrect setup of repository.

My suggestion is:

1. Add "disabled" key into extra column hash (i meant disabled attribute to GitRemote class)
2. Add "disabled" checkbox into settings
3. mark any repository as "disabled" after first SSH fail (user can enable again at any time from settings - then it will check everything just like when creation new repo)

I think that's safer in term of "abuse" warnings.

What do you think?