Made it so that in ARG can be read from a pdb file

This involved splitting the code for reading an argument list from the code
for interpretting it, adding a function for reading the ARG argument from the pdb and
interpretting things like ARG=d1.* to ActionWithArgument and adding a routine
to PDB which allows you to replace the old ARG=d1.* with the newly interpretted
ARG=d1.x,d1.y,d1.z