Older compilers, e.g., GCC 4.4., do not understand the
"simple-type-specifier" syntax of C++11's "friend" declarations.
Typical responses are
error: a class-key must be used when declaring a friend
error: friend declaration does not name a class or function
Restore build on older compilers (e.g., GCC prior to 4.7) by
inserting the 'class' keyword.
This way of refactoring was chosen since the extra term depends
on a lot of context. Instead of recreating the context in the
polymer model (which would not reduce any complexity) the necessary
variables are passed to extraAddWellEq().
Also refactor some functions that are different to call the
base version and then do additional processing. However this
process has not been carried out on all methods at this point.
