Revised peos_init.tcl to source kernel's version first.

The installation procedure copies os/kernel/peos_init.tcl to
kernel_init.tcl, which is then sourced from ajax-cgi/peos_init.tcl.
This means any changes to the kernel's peos_init.tcl (which happens
every time the predicate evaluator is modified) will automatically be
included by ajax-cgi/peos_init.tcl.

These changes were necessary to get diabetes_assessment.pml (which
added) to run.