add "testnet" field to config, and filter those values for "dev build" only

public/data/appConfig.json

@@ -3,6 +3,7 @@
         {
             "type": "ripple",
             "name": "Ripple Testnet",
+            "testnet": true,
             "symbol": "XRP",
             "shortcut": "xrp",
             "bip44": "m/44'/144'/a'/0/0",
@@ -52,6 +53,7 @@
         { 
             "type": "ethereum",
             "name": "Ethereum Ropsten",
+            "testnet": true,
             "symbol": "tROP",
             "shortcut": "trop",
             "chainId": 3,

src/actions/LocalStorageActions.js

@@ -141,10 +141,9 @@ const loadJSON = (): AsyncAction => async (dispatch: Dispatch): Promise<void> =>
     try {
         const config: Config = await httpRequest(AppConfigJSON, 'json');
 
-        // remove ropsten testnet from config networks
+        // remove testnets from config networks
         if (!buildUtils.isDev()) {
-            const index = config.networks.findIndex(c => c.shortcut === 'trop');
-            delete config.networks[index];
+            config.networks = config.networks.filter(n => !n.testnet);
         }
 
         const ERC20Abi = await httpRequest(Erc20AbiJSON, 'json');

src/reducers/LocalStorageReducer.js

@@ -8,6 +8,7 @@ import type { Action } from 'flowtype';
 export type Network = {
     type: string;
     name: string;
+    testnet?: boolean;
     shortcut: string;
     symbol: string;
     bip44: string;