Use the ability_<name> tag for reporting as well as help, so the user
sees readable names including spaces and special chars. (description=
in an ability can't have special chars or spaces, as it's used to look
up <name>_description for help and tooltip).
...remove global assumptions about cure/heal amounts, too.
I also added an explicit number to how much terrain heals (it's still
assumed to cure).
I also separated "cures" and "heals" from the user's perspective,
which unfortunately means the description of "heals" does not include
the number of HP any more. It would be nice if the tooltip could use
variables...
No limit of hitpoints per cure/heal, heal at start of healer turn.
Healing still doesn't stack (you can only be healed by one thing), but
standing next to allies healer can get you double-healing.
If healers are now too powerful, simplest would be to limit number of
patients each healer can treat.
If allied healers are too powerful, we could extend limit across
entire turn, so unit cannot be treated by more than one healer per
turn, even allies.
