Wrap lines automatically at 120 character margin

Problem: bisq-network/style#3 indicates code should be wrapped at 120
characters, but it is likely that people will forget and that this habit
will only change slowly.

Solution: Configure IDEA to wrap lines automatically when typing past
120 characters, forcing the reminder to happen in real time. If this
becomes a nuisance, we can remove it later.

Note that this change also explicitly sets the RIGHT_MARGIN value to
120, even though this is already IDEA's default value. This is simply
to be explicit and self-documenting.