* Add Entry::calculateDifference()
This new function contains the logic that was previously in
EntryHistoryModel::calculateHistoryModifications().
It allows the re-use to display the differences in case of a merge.
* Introduce Database Merge Confirmation Dialog
Adds a dialog allowing a user to review the changes of a merge operation.
This dialog displays the changes and allows the user to abort the merge
without modifying the database.
Fixes#1152
* Added dry run option to Merger
* Changed behavior when actual merge differs from dry run to just output a warning to console
* Fixed KeeShare conflicting with merge operations in the middle of a merge
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Co-authored-by: Jonathan White <support@dmapps.us>
