(U+51F6): Add `ideographic-structure'; add some relations for other

(U+51F6): Add `ideographic-structure'; add some relations for other
characters.
(A-IWDSU+20679): New abstract node.
(A-IWDSU+51F7): Add `<-denotational@component' for A-IWDSU+20679; add
`ideographic-structure'.
(U+51F7): Add some relations for other characters; add representative
nodes.
(U-0002067D): Add `<-denotational@component' for A-compU+20679.
(A-compU+20679): New abstract node; use `<-denotational@component' for
A-IWDSU+20679; add `ideographic-structure'.
(U-00020679): Add A-compU+20679 into a target of
`<-denotational@component'.
(U-0002068B): Apply new conventions for glyph granularity.
(U+2068B-itaiji-001): New character; use `<-denotational' for
U-0002068B.