Node format history and restore

[pleonex]

Sometimes when converting a file we may choose the wrong converter, or we could be trying several. IF the output is not what we expect, we could want to restore the node to its original format (e.g. binary) and try with another converter.
We may also want to inspect its original binary content with the hex viewer even when it's already transformed.

Describe the solution you'd like to see.

• Save the original format of each node so we have a reference after transforming. Do not dispose after transform
• Add a setting value to configure the number of formats to keep so we can undo them
• Implement restore/undo option (via context menu for instance)
• Implement view original hex content (via context menu for instance)