The tiny changes that has been made now every the programmer is able to set multi-model-directory

for example every time that programmer call the following function :

+ $cfg->set_model_directory($another_db_model_path);

the $another_db_model_path will be added to model directory string and in autoloading this directory will be consider when trying to locate mdoles' directory

NOTE: this comes realy help full when developer is working with multi module application and in modules he can use other modules' Models too.
Merge branch 'develop'

Conflicts:
	ActiveRecord.php
	lib/Config.php