Allow to configure particular monitors

[radekk]

There should be a possibility to reconfigure only specific webtask monitor like AWS or Github without going through configuration of all of them. On the other hand there is configuration read from the current config file so user can go through all settings just by hitting the enter key but it's not as fast as it should be. After the number of monitors will reach > 10 it's not going to be easy to reconfigure them without this feature.

gulp configure:webtask aws
gulp configure:webtask github