Name the weapon set that has points available

[lucaskarsten]

Fixes #2119.

Description of the problem being solved:

EstimatePlayerProgress builds the unspent weapon set points warning with the set number written into the format string (Modules/Build.lua:1051):

if not warningsWeaponSet and weaponSet1Used ~= weaponSet2Used then
    InsertIfNew(self.controls.warnings.lines, string.format(
        "You have %d Weapon set 2 passives available",
        math.abs(weaponSet2Used - weaponSet1Used)
    ))
end

The count is fine, since it is the difference between the two sets, but the set is always reported as 2. A character with fewer points allocated in set 1 is told the spare points belong to set 2.

The set with fewer allocated points is the one with room, because a node allocated in both sets is only paid for once — the same reasoning behind normalPassives = PointsUsed - m_min(weaponSet1Used, weaponSet2Used) a few lines above.

Steps taken to verify a working solution:

• Added spec/System/TestWeaponSetPoints_spec.lua covering set 1 behind, set 2 behind, and both equal (no warning). Against dev it reports 2 successes / 1 failure; with the fix, 3 successes / 0 failures.
• Full busted suite: 569 successes / 0 failures / 0 errors.