change map to linked hash to maintain insertion order
delete some old and useless pictures
add default constructor
diff cleanup

diff now uses DiffResult instead of Metrics and TransitionList
add TablesOverVersion to DiffResult
restructure metrics

create new package metrics and move related stuff there.
update sanityCheck for metrics.
add new class TableChanges to hold table changes for each version.
add getters for TableChanges
add main functions for TableChanges
TablesOverVersion now holds a map with table changes over version
remove unused imports
TableOverVersion now holds changes over versions for each table