use proper bytes
structure encoding tests
format an organize imports
rename clone to bytes
create a skeletal Base64DecodeTest
refactor to remove repetition
introduce a set up for Base64DecodeTest
prepare for longer sources to decode
correctly decode different lengths of source 'A'-strings
implement base64 decode
narrow the API of CharacterValues

This is after inspiration of the decode API
set language and target level
depend on hamcrest library
create an inverse theory
create commutative theory
create an Encoder interface
create a Decoder interface