SONARPLUGINS-3028,SONARPLUGINS-1046,SONARPLUGINS-3083,SONARPLUGINS-3348 : enhance the existing crowd-plugin to the same basic featureset and behaviour as the LDAP plugin

* Password check against Crowd
* Synchronization of name (displayName in Crowd) and e-mail address
* Synchronization of relationships between users and groups (authorization) <SONARPLUGINS-1046>
* Authenticate against internal engine if the user was not found in crowd
* Security Realm (Use the "sonar.security.realm" property) <SONARPLUGINS-3028>
* Sonar Crowd should support logging in via JIRA with an embedded crowd server <SONARPLUGINS-3083>
* Make debug logging compatible with SonarQube 4.1 <SONARPLUGINS-3348>

Merge remote-tracking branch 'ferdinandhuebner/master'
Ignore IDEA IntelliJ files
Use sonar plugins parent #18
Don't define a relativePath which isn't always sure to be there
SONARPLUGINS-2931 : Update description in pom
changed : defines all crowd.properties entries manually (probably more things to allow to configure in the future)
SONARPLUGINS-3348 : Sonar 4.1 is required for logs managed by logback