data: Clean up era modifiers in factions file

Each faction has been given era modifiers where appropriate. For
factions that are not explicitly named in CamOps, a comment has been
added indicating which faction's modifiers have been used.

Modifiers for eras before a faction exists are always 0, and modifiers
for eras after a faction dies are left out.

Factions that predate the earliest era with modifiers (that is, factions
that die before 2398) have no modifiers.