MergeDatabase: Database to manage merges
Merger: Setup merge database
MergeOperation: Add merged datestamps property
dateutil.relativedelta: Implement JSON serialization
Merger: Check if a datestamp was already merged
Merger: Keep track of all merged dates
MergedFile: The most recent datestamp should also be deleted
MergedFile: Change datestampToInsert to datestampToUpdate
MergedFile: The datestamp to be updated shouldn't be removed
MergedFile: Fix logic error when removing latest datestamp
Merger: Actually copy files to merge and adapt database

Currently this merged files are copied to a debug directory. The database
itself is altered.