Added IDisabledTrait & UpgradableTrait with upgrade levels support

 * IDisabledTrait for identifying (and filtering) disabled traits
 * UpgradeEnabledDisabledTrait provides an abstract base for enabling by upgrade and disabling by upgrade
UpgradeMaxLevel -> UpgradeMaxEnabledLevel.  There are a few more instances of this, in `mods/ts/rules/structures.yaml`. `mods/ts/rules/infantry.yaml` and the upgrade rules