Fix Android configuration to allow connecting to http://ipfs.singularitynet.io on Android 9+

[vsbogd]

Since Android 9 cleartext connections are forbidden by default, see: https://developer.android.com/training/articles/security-config#CleartextTrafficPermitted

This causes the following NullPointerException error on demo app start:

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.io.InputStream.read(byte[])' on a null object reference
        at io.ipfs.api.IPFS.readFully(IPFS.java:763)
        at io.ipfs.api.IPFS.get(IPFS.java:682)
        at io.ipfs.api.IPFS.retrieve(IPFS.java:662)
        at io.ipfs.api.IPFS.retrieveAndParse(IPFS.java:624)
        at io.ipfs.api.IPFS.version(IPFS.java:572)
        at io.ipfs.api.IPFS.<init>(IPFS.java:69)
        at io.ipfs.api.IPFS.<init>(IPFS.java:45)
        at io.singularitynet.sdk.client.ConfigurationDependencyFactory.<init>(ConfigurationDependencyFactory.java:64)
        at io.singularitynet.sdk.client.Sdk.<init>(Sdk.java:63)
        at com.example.singsplit.SnetSdk.<init>(SnetSdk.java:22)
        at com.example.singsplit.MainActivity.openSingularityNETServiceChannel(MainActivity.java:161)
        at com.example.singsplit.MainActivity.access$300(MainActivity.java:71)
        at com.example.singsplit.MainActivity$OpenServiceChannelTask.doInBackground(MainActivity.java:200)
        at android.os.AsyncTask$3.call(AsyncTask.java:378)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.lang.Thread.run(Thread.java:919)

see similar IPFS issue: ipfs-shipyard/java-ipfs-http-client#125

To fix it:

• add correct network configuration to the Android demo app source code, test it on Android 10
• add this step to the Gradle plugin README.md

[vsbogd]

First task is done by PR #51