Misc refinements

* Refine Kotlin codes;
* Support RTL;
* Use VectorDrawable for notification;
* Remove redundant resources;
* Better IDE integration.

mobile/src/main/java/com/github/shadowsocks/plugin/NativePlugin.kt

@@ -21,12 +21,13 @@
 package com.github.shadowsocks.plugin
 
 import android.content.pm.ResolveInfo
+import android.os.Bundle
 
 class NativePlugin(resolveInfo: ResolveInfo) : ResolvedPlugin(resolveInfo) {
     init {
         assert(resolveInfo.providerInfo != null)
     }
 
-    override val metaData get() = resolveInfo.providerInfo.metaData
-    override val packageName get() = resolveInfo.providerInfo.packageName
+    override val metaData: Bundle get() = resolveInfo.providerInfo.metaData
+    override val packageName: String get() = resolveInfo.providerInfo.packageName
 }