[UWS,TAP] Errors and log management improvements. Particularly, now TAP and...

[UWS,TAP] Errors and log management improvements. Particularly, now TAP and UWS are able to manage correctly HTTP request abortions (i.e. when the user stop the request before the response has been fully sent, or when there is a connection problem or a time-out). Such abortions are considered by UWS and TAP merely as job abortion/cancel. No error is logged any more. In addition of this correction, log entries concerning the execution of a TAP sync/async job have been modified so that having more coherents messages. And stack traces of exception that occurred when executing a job (sync or async, tap or uws) are displayed just once: at the JOB END log entry, and not by the HTTP RESPONSE_SENT entry. And finally, output flush and interruption detection are made more often when writing a query result (the flush is particularly important when combining with fetch-size > 0 in synchronous mode....the sync response is then a streaming output).