Added option to change data folder location. (#17)

Removed commonDirectory.
Removed instanceDirectory.
Added dataDirectory. The common and instance directories are now resolved from this.
The config.json and distribution.json are now stored in Electron's data folder (app.getPath('userData')).
Users can edit the dataDirectory under launcher settings.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "westeroscraftlauncher",
-  "version": "1.4.2",
+  "version": "1.5.0",
   "productName": "WesterosCraft Launcher",
   "description": "Modded Minecraft Launcher",
   "author": "Daniel Scalzi (https://github.com/dscalzi/)",
@@ -12,7 +12,7 @@
   "private": true,
   "main": "index.js",
   "scripts": {
-    "start": "electron index.js",
+    "start": "electron .",
     "cilinux": "electron-builder --linux --win",
     "cidarwin": "electron-builder --mac",
     "dist": "cross-env ELECTRON_BUILDER_ALLOW_UNRESOLVED_DEPENDENCIES=true electron-builder",