Add log in sonar.log when migration is required and CE is waiting for SQ

Since Web and CE processes now log in their own files, when a DB migration is required, it is not visible in sonar.log that SQ startup is on hold and waiting for a DB migration.

Therefor one log line should be added to indicate in sonar.log that a DB migration is required and another one should be added to explain that CE's startup is on hold until this migration is done (because the message Process[ce] is up won't be displayed until then).

This limitation exists in 6.2-RC1.