Exceptions

[koczkatamas]

Currently One does not support real exceptions, only raising one-shot ~fatal error.

To support exceptions the following scenarios have to be planned out:

• Support languages which does not have exceptions, but you have to return error code / object instead of throwing exception. This changes the code flow significantly.

• Track which methods throw exception, this probably requires an independent stage of some depth-first search with some logic for circle / recursion detection