Allow fully qualified enum, class, structs titles

[5p4k]

I have items with the same name in different namespaces, e.g. device1::error and device2::error. When generating the full unabridged API, I get two entries both named "Enum error" (as it should be). However in this specific case, it is confusing. I tracked this down to https://github.com/svenevs/exhale/blob/ebad897acd4f4aeef4303b0fa55873dd840aba89/exhale/graph.py#L2503

I would like to be able to produce fully qualified titles for this project. This could very well be a project-level option (having only some items fully qualified may be even more confusing).

I think I could also provide a PR implementing this by adding a page-level customization option fullyQualifiedTitles, if that's the way to go about this.

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On a side note, thank you for all the work put in this project. I got back to this after some years and it had matured so much that I'm now switching over from plain Doxygen:)