Windows-definitions-schema.xsd update

updated windows-definitions-schema.xsd under the
oval-def:EntityStateStringType with the following:
reg_dword_little_endian
reg_dword_big_endian
reg_link
reg_qword_little_endian
windows-system-characteristics-schema.xsd update

updated windows-system-characteristics-schema.xsd under the
oval-sc:EntityItemRegistryTypeType with the following:
reg_dword_little_endian
reg_dword_big_endian
reg_link
reg_qword_little_endian
windows-definition-schema.xsd update

updated registry_item datatype value entity documentation to include
REG_DWORD_LITTLE_ENDIAN
REG_DWORD_BIG_ENDIAN
REG_LINK
REG_QWORD
REG_QWORD_LITTLE_ENDIAN
windows-system-characteristics-schema.xsd

registry_item datatype value entity documentation to include
REG_DWORD_LITTLE_ENDIAN
REG_DWORD_BIG_ENDIAN
REG_LINK
REG_QWORD
REG_QWORD_LITTLE_ENDIAN
Merge pull request #138 from LuisNunez/master

#102