Minor code and documentation corrections:

Minor code and documentation corrections:

* Use cStringIO to have better performace
* Corrected doc strings
* Hooks system: create a getHookFunction on the Addon class so the calable can be retrived
* Hooks system: when running a hook on all loaded addons return (addon, ret) even if the hook returns None, so callers can check what addons realy implemented the hook.
* Many more small corrections (see #213, comments 37 to 41).