OPENDJ-902 (CR-1702) Add connectionID to the HTTP access log + move to extended log format
OPENDJ-858 (CR-1702) Add stats tracking to HTTP client connections



In HTTP access log, changed the name of the non standard "datetime" field to "x-datetime".
Added the "x-etime" field that outputs as a number.
Added validation for the log format that outputs error messages.


FileBasedHTTPAccessLogPublisherConfiguration.xml, FileBasedHTTPAccessLogPublisherConfiguration.properties:
Renamed the "datetime" field to "x-datetime" + added the "x-etime" field.
Improved the description of the ds-cfg-log-format.

TextHTTPAccessLogPublisher.java, config.properties:
Extracted constants for all supported field names.
Added ALL_SUPPORTED_FIELDS constant.
Changed logFormatFields instance member from String[] to List<String>.
Added validateLogFormat() which can output new error messages and called it from applyConfigurationChange() and initializeLogPublisher().
Added subtract().

HTTPClientConnection.java, HTTPRequestInfo.java:
Added instance member totalProcessingTime.
In sendResponse(), added to the totalProcessingTime + extracted method getProcessingTime().
Added getTotalProcessingTime().