Merge branch 'invis_fix' into 'master'

Invisibility floating point fix

Adjusts several stealth and invisibility granting talents/effects/artifacts (Invisibility, Ethereal Rune, Hymns, Projection, etc.) to always round their granted stealth/invisibility powers (attributes `stealth` and `invisible`). This constitutes a very slight buff to these effects, but addresses a fairly common issue most often seen on Shalore where floating point errors will accumulate when multiple invisibility effects are applied. The resulting `A + B - B - A ~= 0` error will cause permanent invisibility at very low power ( ~10^-15 ), along with an obnoxious screen and actor shader.

Stealth didn't suffer from this issue as only two effects grant `stealth`, but was changed for consistency.

This MR also fixes a bug in the description of Projection; the granted stealth/invisible detection power was half what the description wrote. The description was adjusted to match the actual behavior.

**This MR is save safe**, although bugged games and actors already under the effects of a modified talent won't update until the effect is applied.

See merge request !702