[enh] update TODO
[mod] update TODO
[enh] put LineProxy on ClassNode
[enh] put LineProxy on ElifNode
[enh] put LineProxy on ElseNode
[enh] put LineProxy on ExceptNode
[enh] put LineProxy on FinallyNode
[enh] in fact, put LineProxy on every CodeBlockNode, way faster, safer
[mod] remove duplicated code
[mod] update TODO
[mod] update TODO
[enh] fix all bugs related to defaulting to LineProxy everywhere