Clean/move/rename/refactor code

android/gradle.properties

assets/translations/en.json

assets/translations/fr.json

fastlane/metadata/android/en-US/changelogs/28.txt

fastlane/metadata/android/fr-FR/changelogs/28.txt

lib/main.dart

lib/models/counts_by_day.dart

lib/models/counts_by_hour.dart

lib/models/discoveries.dart

lib/models/statistics_global.dart

lib/models/statistics_recent.dart

lib/models/timeline.dart

lib/models/topartists.dart

lib/network/scrobbles.dart

lib/ui/screens/discoveries.dart

lib/ui/screens/home.dart

lib/ui/screens/statistics.dart

lib/ui/skeleton.dart

lib/ui/widgets/abstracts/custom_bar_chart.dart

lib/ui/widgets/abstracts/custom_line_chart.dart