Parse version manifest and download forge libraries.

TODO:
Integrate base url propagation.
Integrate PackXZExtract to calculate hashes  of jar.pack.xz files.
OR ammend the distribution spec to accept different hash algos (requires helioslauncher update).

src/model/forge/versionmanifest.ts

@@ -0,0 +1,20 @@
+export interface VersionManifest {
+
+    id: string
+    time: string
+    releaseTime: string
+    type: string
+    minecraftArguments: string
+    mainClass: string
+    inheritsFrom: string
+    jar: string
+    logging: any
+    libraries: Array<{
+        name: string,
+        url?: string,
+        checksums?: string[],
+        serverreq?: boolean,
+        clientreq?: boolean
+    }>
+
+}