Weak Portal Plugin

At a glance high level indicator of portals in disrepair. Opacity is
used to denote how much it's hurting. (Bright means needs the most
attention.) Factors in current energy, missing shields, or missing
resonators. Red means it needs attention. Orange means the same thing,
except that it's down at least one resonator.

I realise this is in opposition to game convention where dim == almost
dead, but I tried it that way, and it just made no sense to me to do it
that way. The whole point is a high level way to quickly identify
portals that most need repairing. If opacity isn't done this way your
eyes are most drawn to the portals that least need your attention.