add cordova-android bintray upload to release process

Uploading to bintray has been added to cordova-android. https://github.com/apache/cordova-android/pull/361

We need to add these steps to the platforms release process.https://github.com/apache/cordova-coho/blob/master/docs/platforms-release-process.md

coho also need to update the version number in build.gradle during prepare-release-branch command. https://github.com/apache/cordova-android/blob/master/framework/build.gradle#L43