There are now three possible code entries for the scalarCodedSource,
vectorCodedSource, etc..., fvOptions. These are `codeAddSup` for basic
sources, `codeAddRhoSup` for compressible sources, and
`codeAddAlphaRhoSup` for phase (compressible) sources.
Previously `codeAddSup` was used for both basic and compressible
sources, and phase sources were not implemented. This meant that whilst
a compressible source could be created, it could not make use of the
`rho` argument or the basic source function would fail to compile.
Most fvOptions change the state of the fields and equations they are applied to
but do not change internal state so it makes more sense that the interface is
const, consistent with MeshObjects. For the few fvOptions which do maintain a
changing state the member data is now mutable.
The dynamic code functionality has been generalised so that the names of
the code entries in the specifying dictionary can be set by the caller.
This means that functions which utilise dynamic code but use different
entry names (e.g., codedFunctionObject uses codeExecute, codeEnd,
etc..., instead of code) now function correctly. The differently named
entries now form part of the library hash, and re-building triggers
appropriately as they are modified.
