Nerudite Armor Rebalance idea 2

There's been much discussion of Nerudite Armor lately. Here is one idea
for changing how the armor works:

- Changed nerudite resistances from individual to ATCK_SPELL_ALL. This
means it will no longer stack with rings, and it will also help against
holy and unholy. The only thing this new nerudite armor will stack with
is Resist Magic. The new value for this "all spell" resistance is 10%.
The armor is still vulnerable to quake damage by a sum of -20%.

Together, Nerudite Armor and Resist Magic will add up to 35% "all spell"
resistance. This will cut damage of spell attacks by roughly a third.
The majority of this resistance (25%) is from Resist Magic, which can be
purged, weapon proc purged, or timed out (max duration 4 minutes).
Compare to elemental resists which last up to 8 minutes.

Elemental resists + rings will add up to 45% resist to their respective
element, still remaining superior to Nerudite + Resist Magic's 35%.

This should take much of the emphasis off of nerudite armor and resist
ring switching during combat. Without Nerudite Armor's individual
resists, Resist Magic trumps rings now (25% > 20%), so wearing rings is
pointless if you have Resist Magic. Rings will likely be relegated to
builder protection or stacking with elemental resists for Faren mages.