fix -Wshadow warning in StarSystem.cpp
modify scan_enums so that it explicitly converts values to int in its data

This is necessary when generating tables for strongly typed enums
(that is, the 'enum class' syntax), because they don't have an implicit
conversion to int.
remove various unused methods and variables
remove ShipType::equipSlotCapacity array
update documentation comment for Lua Timer:CallEvery
add missing include in Lang.h
remove unnecessary includes of EquipType.h
strip out EquipType; create simpler replacement for sysgen to use
include star system trade levels in the galaxy dump output
reintroduce a bug to avoid changing galactic trade levels and population
copy the EquipSlot doc comment to libs/Equipment.lua and update it
remove two unused fields from the galactic economy/commodity data
start keeping a record of things that should be fixed at the next save bump
Merge remote-tracking branch 'jpab/remove-core-equip'