Make logs more automatic-parse friendly

[SmiSoft]

system/classes/Kohana/Log.php

• shortens path using Debug::path to prevent site owner (viewing logs) from long (sometimes, very long) paths;

system/classes/Kohana/Log/Writer.php

• unify log filenames for regular logs (from normal application execution) and from exception handling (regular log procedure call generate log in form "message in file.php:123", but excptions generate log in format "message ~ file.php [123]"). I use automatic log's analyzer, so it's quite inconvinient to create different patterns for different log's messages;