Add functions atk_role_get_name() and atk_role_for_name() which transform

Add functions atk_role_get_name() and atk_role_for_name() which transform

* atk/atkobject.[c|h]:
Add functions atk_role_get_name() and atk_role_for_name() which
transform a role into an untranslated string
Update comments in atkobject.h which refer to property names

* atk/atkrelation.c:
Correct error in atk_relation_type_get_name

* docs/atk-sections.txt
Added atk_role_get_name and atk_role_for_name

* docs/tmpl/*sgml
Updated files