Fix typo and small bugs, remove Kohana::version

Bugs:

https://github.com/kohana/core/blob/3.4/develop/classes/Kohana/Core.php#L255
https://github.com/kohana/core/blob/3.4/develop/classes/Kohana/Core.php#L258
~~~
mkdir($settings['cache_dir'], 0755, TRUE);
~~~
~~~
chmod($settings['cache_dir'], 0755);
~~~
low chmod

https://github.com/kohana/core/blob/3.4/develop/classes/Kohana/Core.php#L442
~~~
if (is_array($value) OR is_object($value))
~~~
incorrect condition: is_object($value)

https://github.com/kohana/core/blob/3.4/develop/classes/Kohana/Core.php#L1025
~~~
if (Kohana::$errors AND $error = error_get_last() AND in_array($error['type'], Kohana::$shutdown_errors))
~~~
incorrect condition: error_get_last() return array or null

https://github.com/kohana/core/blob/3.4/develop/classes/Kohana/Core.php#L1028
~~~
ob_get_level() AND ob_clean();
~~~
incorrect condition: ob_get_level()  return integer

Delete Kohana::version(): this method is not used.