Add support for processing 1.12.2 Forge compiled with Forge Gradle 3 (#8).

Changed the resolver names to match the Forge Gradle versions, since that software version
determines the structure of the jar file and how it needs to be parsed.
Refactored the ForgeGradle3 resolver to conditionally execute the installer only when we
need artifacts generated by the installer. This allows the new 1.12.2 builds to be processed
without running the installer.
Changed the VersionSegemented interface to accept a libraryVersion, so we can segment within
a minecraft version.

This change is pending verification with Helios.

package.json

@@ -28,10 +28,10 @@
   "devDependencies": {
     "@types/adm-zip": "^0.4.33",
     "@types/fs-extra": "^9.0.1",
-    "@types/node": "^12.12.42",
+    "@types/node": "^12.12.43",
     "@types/yargs": "^15.0.5",
-    "@typescript-eslint/eslint-plugin": "^3.0.2",
-    "@typescript-eslint/parser": "^3.0.2",
+    "@typescript-eslint/eslint-plugin": "^3.1.0",
+    "@typescript-eslint/parser": "^3.1.0",
     "eslint": "^7.1.0",
     "rimraf": "^3.0.2",
     "typescript": "^3.9.3"