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
+    }>
+
+}

src/model/struct/model/module/module.struct.ts

@@ -43,8 +43,8 @@ export abstract class ModuleStructure extends BaseModelStructure<Module> {
             for (const file of files) {
                 const filePath = resolve(this.containerDirectory, file)
                 const stats = await lstat(filePath)
-                const buf = await readFile(filePath)
                 if (stats.isFile()) {
+                    const buf = await readFile(filePath)
                     const mdl: Module = {
                         id: await this.getModuleId(file, filePath, stats, buf),
                         name: await this.getModuleName(file, filePath, stats, buf),

src/model/struct/repo/BaseMavenRepo.ts

@@ -15,8 +15,8 @@ export abstract class BaseMavenRepo extends BaseFileStructure {
         super(absoluteRoot, relativeRoot, structRoot)
     }
 
-    public getArtifactById(mavenIdentifier: string): string | null {
-        const resolved = MavenUtil.mavenIdentifierToString(mavenIdentifier)
+    public getArtifactById(mavenIdentifier: string, extension?: string): string | null {
+        const resolved = MavenUtil.mavenIdentifierToString(mavenIdentifier, extension)
         return resolved == null ? null : resolve(this.containerDirectory, resolved)
     }
 
@@ -30,9 +30,17 @@ export abstract class BaseMavenRepo extends BaseFileStructure {
         return pathExists(path)
     }
 
-    public async downloadArtifact(url: string, group: string, artifact: string, version: string,
-                                  classifier?: string, extension?: string) {
-        const relative = MavenUtil.mavenComponentsToString(group, artifact, version, classifier, extension)
+    public async downloadArtifactById(url: string, mavenIdentifier: string, extension?: string) {
+        return this.downloadArtifactBase(url, MavenUtil.mavenIdentifierToString(mavenIdentifier, extension) as string)
+    }
+
+    public async downloadArtifactByComponents(url: string, group: string, artifact: string, version: string,
+                                              classifier?: string, extension?: string) {
+        return this.downloadArtifactBase(url,
+            MavenUtil.mavenComponentsToString(group, artifact, version, classifier, extension))
+    }
+
+    private async downloadArtifactBase(url: string, relative: string) {
         const resolvedURL = resolveURL(url, relative).toString()
         console.debug(`Downloading ${resolvedURL}..`)
         const response = await axios({