This commit switches from `deduplicateNames`, which changed certain
`CustomName` values, to `promoteOriginalName`, which updates empty
`CustomName` using non-ambiguous versions of `OriginalName`.
Model classes are now described by a YAML document, which is used to
generate C++ headers containing classes and all the boilerplate
required for YAML serialization/deserialization, usage in
SortedVectors, etc. See the README in include/revng/Model for more
info.
Ivan Krysak