Sitecore 9.2+ support

[markgibbons25]

Right, so I think I've sorted out what's going on here:

• Sitecore 9.2 has refactored the Job API a bit so current implementation wouldn't work but could be easily fixed
• At some point the built-in ReferenceReplacementJob seems to be changed to support clones only - so this job no longer works for "smart copy" or "smart duplicate", it would only work for "smart clone"
• I have fixed that by copying the ReferenceReplacementJob code and modifying it slightly to not do hardcoded checks for item.SourceUri which is only available on clones.
• The PR Job ReferenceReplacementJob is obsolete, Replacing it with running pipeline "replaceItemReferences", also creating helper method to update links when creating items of branch templates #6 seems to address fixing the Job API refactor, and also adds in some code to support updating layout fields on branch template copies. However I tested this on Sitecore 10.0 and it (updating layout fields on branch template copies) isn't required as the ReferenceReplacementJob does this too.

I would open a PR, however I'm only interested in the Smart Copy and Smart Duplicate , and so won't have tested Clone, and also am unsure as to why this ReferenceReplacementJob used to work and doesn't now so would be good to figure out exactly which version this was changed.