in generated c++: in constructors, populate iAttrs

is populated with inverse attrs, setters, getters
in generated c++: ensure that pointers are zeroed (DataMemberInitializers())
use DataMemberInitializers() to initialize members in generated c++
in generated c++: ensure pointer is non-null before calling shallowCopy
in generated c++: create data members for null pointers
eliminate unused buffer
improve some comments for doxygen
use InstMgrBase instead of InstMgr in most stepcore classes

this is so that lazyInstMgr functions will be called when necessary
whoops, don't pretend an instance can't be found if it is already loaded
update inverse attr test 3
forgot to replace InstMgr with InstMgrBase in selects.c
oops, didn't add param to fn proto or call in selects.c
when printing initializers, skip derived attrs
forgot to add 'const' keyword in several places after changing the ..._get_head() fn
split entity methods out of ATTRprint_access_methods into 2 new funcs

second new func prints log stuff, called by other func 3x
replace entity access member code with call to new func
fix a few comments
formatting
macro CONST -> const