Improvements for integration with LDAP

Use cases :

• If LDAP not available (connection problem, etc), then fallback to SonarQubeDatabase.
  
  • SONAR-3138
• Manual creation of local accounts (which does not exist in LDAP) : set all fields (login, password, full name, email).
  
  • SONAR-3138
• Manual creation of external accounts: set login, all other fields should come from external system.
  
  • SONAR-3137
  • Warning message about passwords.
• Automatic user creation.
  
  • Already implemented - SONAR-1334 , but should be tuned - SONAR-3137 and SONAR-2292
• Manual creation of local groups (which does not exist in LDAP) : set name, members.
  
  • Already implemented.
• Manual creation of external groups: set name, members of this group should be determined automatically from external system.
  
  • SONAR-2292