Change submodule from owncloudChalmers/android-library to owncloud/android-library

owncloud/android#661 got merged too quickly after owncloud/android-library#38 so we did not have time to update the submodule to point to the organization repository.

Please note that this is pointing to develop because Gradle cannot use a submodule which does not support Gradle, and develop is the branch that supports it right now.