Distribute client through maven

[adamKasapakis]

Currently we are recommended in your integration guide to download the client from https://developer.fiskaly.com/downloads and copy the aar to the project.
From Android Gradle plugin version 4.0.1 (gradle-6.1.1) the build is failing because gradle doesn't allow to copy libraries in the project
We are trying to upgrade gradle and we get the following error:

Direct local .aar file dependencies are not supported when building an AAR. The resulting AAR would be broken because the classes and Android resources from any local .aar file dependencies would not be packaged in the resulting AAR. Previous versions of the Android Gradle Plugin produce broken AARs in this case too (despite not throwing this error). The following direct local .aar file dependencies of the :saleslib project caused this error: /home/jenkins2/slave/workspace/.../libs/com.fiskaly.client-android-all-v1.2.000.aar

We need to get the client from a repository as it is done for the SDK. This, apart from following the android industry standard of importing libraries will unblock us from upgrading gradle plugin in our project.

Details:
We are using the Client in an Android Studio Module and not in the main project