If there is an exception in the template handling then a white page is shown.
This improves the handling of this and shows text only about the internal
error.
To test this just setup redis as cache and then disable the php-redis module.
Signed-off-by: Morris Jobke <hey@morrisjobke.de>
Otherwise `null` is returned which leads to a ton of similar error messages if the log condition setting is enabled.:
```
{"reqId":"3wVBarnDfOV3qkI1bVCU","remoteAddr":"89.98.78.41","app":"PHP","message":"hash_equals(): Expected user_string to be a string, null given at \/var\/www\/html\/lib\/private\/Log.php#275","level":3,"time":"2016-10-07T14:22:15+00:00","method":"PROPFIND","url":"\/remote.php\/webdav\/","user":"icewind"}
```
- Updated the config sample to point to log_type='file'
- Renamed the Class for logfile logging to File in namespace 'OC\Log\'.
Changed the occurrences of 'OC\Log\Owncloud' to 'OC\Log\File'.
- Renamed the Class for log:file command to File in namespace 'OC\Core\Command\Log\File'.
Changed registration of the command to use 'OC\Core\Command\Log\File'.
- Changed default Syslog tag to Nextcloud
- Retained backwards compatibility for configs with 'logtype' => 'owncloud'
- Adjusted tests for the new file log.
Closes#490.
