$Revision: 0.7 $
- Documentation review (again and again and again)
- Attribute that isn't changable after first set call to it
- Allowed value 'undef'
- A better system to allow/deny values:
  - with deny counterparts
  - uses less (just one) global variables
  - documents better
- A better system for default values:
  - supports static assignements
  - supports dynamic assignements
  - documents better
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