API server logs shall be stored in Elasticsearch

[ekazachkova]

The current PR provides implementation for issue #1795

The following changes were added:

• a new fields added to log filter object: classNames, threadNames and severities
• a new fields added to log entry output object: className, threadName and stacktrace
• a new fields threadNames and severities added to GET log/filter method output
• elasticsearch index name changed from security_log to application_log. This index contains all logs: security and application. The type can be resolved by type field
• a new log file application.json will be created. This file contains all logs expecting security logs
• application.json file added to filebeat configuration