//- Does the surface need an update?
        virtual bool needsUpdate() const = 0;

        //- Mark the surface as needing an update.
        //  May also free up unneeded data.
        //  Return false if surface was already marked as expired.
        virtual bool expire() = 0;

        //- Update the surface as required.
        //  Do nothing (and return false) if no update was required
        virtual bool update() = 0;

    The constructors for the derived classes should generally start in a
    'expired' condition (ie, needsUpdate() == true) and rely on a subsequent
    call to the update() method to complete the initialization. Delaying the
    final construction as late as possible allows the construction of
    surfaces that may depend on intermediate calculation results (eg,
    iso-surfaces) and also avoids the unnecessary reconstruction of surfaces
    between sampling intervals.

    It is the responsibility of the caller to ensure that the surface
    update() is called before the surface is used.  The update() method
    implementation should do nothing when the surface is already up-to-date.

- version is WM_PROJECT_VERSION prefix + SHA1 from current git head
- move double quotes from make rules to global.Cver for extra safety

- added wmakePrintBuild -check, -update, -version options
- only update .build cache when explictly requested and
  from within the wmake Cver rules
- use -check option to avoid unnecessary remake in src/Allwmake

- the $WM_PROJECT_DIR/.build file is automatically updated.
  This file is (and must be) ignored by git.

- This was originally plan 'B', but it is actually probably more efficient
  than using PtrDictionary anyhow.
- straightened out the return value logic, but it wasn't being used anywhere
  anyhow.
- new 'updated_' data member avoids inadvertent execution in the read()
  method when execution is turned off.

Conflicts:

	src/Allwmake
	src/OpenFOAM/global/global.C
	wmake/rules/General/version

Retained solution with global.Cver

- move url to lower right: makes version information stand out better

New fuels are iso/n-propanol and urea.  Although urea is a bit dodgy, but that's
all of the properties Ive found so far.

I've also added a variation of temperature instead of constant temperature for
some injector-classes so Im sending you the new version of the dieselFoam
tutorial also.

- PtrDictionary and remove(const word&) does not seem to work

- can return NULL pointer instead of FatalError for non-existent entries

- The new cmake seems to be even smarter. If we try to use env variables in
  the .cmake files (eg, with And's sed fixup), they are rewritten in a
  subsequent re-make and take much longer).  Adjusting the compiler values
  themselves causes a full remake. On the positive side, disabling the rpath
  seems to mean we may not need any of this.

  In summary - yuck!