Disable group syncing from crowd server

[andreasebling]

Added new key for the sonar.properties file: crowd.groups.sync (true/false) If false, the groups are not synced from the crowd server. Defaults to true.

[scmbuildguy]

Great addition and the changes work for me. It was frustrating to have my authentication set to Crowd and since I do not manage sonar groups through Crowd the groups reset on each login for the user. Now I am able add users to SonarQube groups and they persist when the user logs in. I hope this can be in the next release

[sogecap]

looking forward to have in version 2.1