OpenFOAM field reading: Automated the handling of <field>.orig files

Now if a <field> file does not exist first the compressed <field>.gz file is
searched for and if that also does not exist the <field>.orig file is searched
for.

This simplifies case setup and run scripts as now setField for example can read
the <field>.orig file directly and generate the <field> file from it which is
then read by the solver.  Additionally the cleanCase function used by
foamCleanCase and the Allclean scripts automatically removed <field> files if
there is a corresponding <field>.orig file.  So now there is no need for the
Allrun scripts to copy <field>.orig files into <field> or for the Allclean
scripts to explicitly remove them.

tutorials/multiphase/reactingTwoPhaseEulerFoam/RAS/bubbleColumnPolydisperse/Allrun

@@ -7,10 +7,9 @@ cd ${0%/*} || exit 1    # run from this directory
 # Set application name
 application=`getApplication`
 
-cp 0/alpha.air.orig 0/alpha.air
-cp 0/f.air.bubbles.orig 0/f.air.bubbles
-
 runApplication blockMesh
 runApplication topoSet
 runApplication setFields
-runApplication $application
+runApplication $application
+
+#------------------------------------------------------------------------------