- Remove util.BASE64, make clients use io.Base64.

- Rename core to common?
- Split up into three sub modules?
  - common-core
    - lang
    - util
  - common-io
    - io
    - io.enc
    - io.ole2 (or move to separate module?)
    - net (or move to separate module?)
    - xml (or move to separate module?)
  - common-image
    - image
  - common-sandbox
    - all unreleased/experimental stuff

- Test cases for the OLE2Compound stuff
- Test cases for encoder/decoders
- Test cases in general
