Tahoe Code SVN development

added flags to indicate materials have history variables

cleaning up some functions

cleaned up memory management

(1) initialize some pointers to NULL
(2) name change natural_bc -> aps_natural_bc to avoid collision with
natural_bc defined in ContinuumElementT

fixed access default exception, but now get malloc

modified xml input format

get access fault exception in APS_AssemblyT destructor when run as -xsd in CW

small strain enhanced strain localization element updated for xml

compiles but not working

Bus error when run "tahoe -xsd"

corrected removing lambda degrees of freedom from center nodes

syntax needs to be changed because variables are now pointers to fields, not
fields themselves