Classes: dup and dups

[russHyde]

PLAN: conversion of dupree output into Dups object

• - rewrite all tests that use output from dupree*() functions to test on as.data.frame(dupree_*()) rather than on the actual return values.
• add Dups class (just wrap the data.frame)
• add as.data.frame.Dups()
• rewrite dupree() to return a Dups object

Conversion of Dups[data.frame] into Dups[list(Dup)]:

• TODO

[russHyde]

Want a lightweight class Dup for storing block-to-block duplication information.

Want a container class Dups for storing [block-to-block pairs, individual block data, (?) cluster data]

dupree[_dir|_package] should return a Dups object

• this should have an as.data.frame.Dups and a print.Dups method
• (try to ensure the printed data-frames look the same in the README after introducing the classes)