Remove DataMapperWrapper
Extract parts of Store-class into Data
Straighten up Data class

Add a bit more structure to get a view on the general
pattern of the methods.
Revert "Straighten up Data class"

This reverts commit 58b1502d1f624b1bf5bf007ee775df44ea325b50.
Revert "Extract parts of Store-class into Data"

This reverts commit e0402b9cdd4435c84c88a2b8a6273e18fb0ab2ae.
Add version hint to README