By Jan Strupczewski BRUSSELS (Reuters) - Euro zone finance ministers will discuss on Monday how to keep Greece financed during the time it will need to agree a third bailout, but none of the options under consideration appear easy, officials said. "The big issue for today is going to be bridge financing and I foresee those negotiations being very difficult because I don't see many countries having a mandate to give money without any conditions," said Finnish Finance Minister Alexander Stubb. ...