Extend the interface of OilVaporizationProperties to not rely on
checking the enum for existence checks. This facilities checking
hasOilVaporizationProperties which rely on DynamicState.size.
OilVaporizationProperties can now be default constructed, and its
storage has been changed from shared_ptr to value (which mandates the
support for default construction and equality/unequality).
The default constructed Property is considered unspecified and
operations on it will not make sense.
Every header is self-contained and includes only what it must to
function, relying on users include what they need in source files,
adopting a pay-what-you-use model (in particular for internal
dependencies).
This is an effort to improve build performance. Several includes
scattered across the project are either unused or partially used (i.e.
just used to import a type name, not depending on the actual contents of
the header file).
Replaces a lot of these includes with forward declarations.
