WIP: filter for all one-off

[btrd]

fix #799

[btrd]

From my local test, it doesn't work :(
Maybe the log-service doesn't allow this filter ?

[EtienneM]

Currently our backend does not support this syntax. Is there a reason that the customer don't use grep? I mean, it should be possible to do:

scalingo --app my-app logs | grep one-off

WDYT?

[btrd]

• to prevent from having to download every log lines
• grep doesn't work when using -f
• if web & web-1 if valid, there is no reason (from the point of view of the client) that one-off-1 work but not one-off

I think we can close this PR, I let you decide what to do with the issue.

[btrd]

Need a change in https://github.com/Scalingo/logs-service to work.