The Clang compiler does not use std::move to transfer the result of the ternary
operator into the phase-fraction field resulting in it not being registered to
the database. To work around this limitation/bug the ternary operator is now
provided with tmp fields the result of which is passed with an IOobject to the
final field constructor to ensure it is registered and the IO options set
correctly.
This change makes multiphaseEuler more consistent with other modules and
makes its sub-libraries less inter-dependent. Some left-over references
to multiphaseEulerFoam have also been removed.
