refactor(validation): move data validation and null checks from sender strategies to sender client to fail fast

refactor(config): print error with all available environments if the configured active environment is missing

- Rework der Applicationconfig zu yaml

Feature/15 Java SDK MVP Part I: contains implementations for sending & subscribing to submissions, adds commandline client

#414 remove comment since the exception class names describe what kind of unexpected behaviour they cover

#414 Refactor sender client, add all calls to the sender facade and reduce the number of steps to send a submission. Also do the authentication implicitly.