Add abstract characters and relations about BUCS.

Add abstract characters and relations about BUCS.
(U+4ECA): Use `->denotational' to separate representative node.
(GT-00487): Add `<-denotational' for U+4ECA.
(U+4F53): Use `->denotational' to separate representative node.
(M-00540): Add `<-denotational' for U+4F53; add `<-vulgar' for
J0-424E.
(U-000201DE): Use `->subsumptive' to separate representative nodes.
(GT-00767): Delete `morohashi-daikanwa'; add `<-simplified@component'
for U+50C9.
(GT-K3992): Use `<-denotational' for GT-00767; add
`<-formed@component/connect-right' for GT-00767.