Fall back to default log file if logfile config file not found, suppress writing errors, fixes issue #826

Thanks Bart for the hint.
This also switches "==" to "<>" and not the code actually works ;-)

https://github.com/owncloud/core/issues/504

fix utf8 filenames in ie download response header according to rfc5987, see http://stackoverflow.com/questions/93551/how-to-encode-the-filename-parameter-of-content-disposition-header-in-http

Fall back to default log file if logfile config file not found, suppress writing errors, fixes issue #826

Thanks Bart for the hint.
This also switches "==" to "<>" and not the code actually works ;-)

https://github.com/owncloud/core/issues/504