Fix #2963

Changed all file permissions settings throught the framework
and the documentation.

Also added configuration settings for CI_Log and CI_Image_lib
diff --git a/system/libraries/Cache/drivers/Cache_file.php b/system/libraries/Cache/drivers/Cache_file.php
index aa2e8fa..2989804 100644
--- a/system/libraries/Cache/drivers/Cache_file.php
+++ b/system/libraries/Cache/drivers/Cache_file.php
@@ -92,7 +92,7 @@
 
 		if (write_file($this->_cache_path.$id, serialize($contents)))
 		{
-			@chmod($this->_cache_path.$id, 0660);
+			chmod($this->_cache_path.$id, 0640);
 			return TRUE;
 		}