Immediate TODO list
-------------------

- Herve: Make the MaskCollection class a derivative of the SimpleIRangesList
  class.

- Herve: Use a different name for "reverse" method for IRanges and
  MaskCollection objects. Seems like, for IRanges objects, reverse()
  and reflect() are doing the same thing, so I should just keep (and
  eventually adapt) the latter. Also, I should add a "reflect"
  method for SimpleIRangesList objects that would do what the current
  "reverse" method for MaskCollection objects does.
  Once this is done, adapt R/reverse.R file in Biostrings to use reflect()
  instead of reverse() wherever needed.

- Clean up endomorphisms.


Long term TODO list
-------------------

o RangesList:
  - parallel rbind
  - binary ops: "nearest", "intersect", "setdiff", "union"
    - 'y' omitted: become n-ary ops on items in collection
    - 'y' specified: performed element-wise
  - unary ops: "coverage" etc are vectorized
    
o DataTable:
  - group generics (Math, Ops, Summary)
  
o SplitDataFrameList:
  - rbind

o IO:
  - xscan() - read data directly into XVector objects

