Alberta phase3 inventory

The Alberta phase 3 inventory is accompanied by a set of
mensurational equations.  These are coded up in the file
'phase3.tcl'.  The equations rely on a set of coefficients
that are loaded in the file 'coef.rul'.

Test this out by sourcing the script 'phase3.tcl'.

The variable 'date' is a key driving variable.  Changing the
value of 'date' will cause the values of most of the variables
to change.