Allow Online Installer to setup Android environment

The current workflow for Qt users targeting Android (or who want to build Qt for Android) is the following:

• Install a Qt for Android version from installer
• Manually download the Android SDK, Android NDk, install required packages, potentially install an AVD.
• Or use Android Studio to download the SDK, NDK and other packages
• Qt Creator "Setup SDK" to download the SDK, NDK and other packages.

However, all of those methods are not fully automatic, some semi-automatic. It would be much more user friendly, to have the Installer setup the Android environment when an Android version for Qt is selected. Then, the user would straight go to using that. The advantage of that also is that we could control which version of each package to use with for Qt, and notify for updates when ready.