TODO

* Implement the rest of ASN.1 types (Real etc)
* Specialize ASN.1 character and useful types
* Come up with simpler API for deeply nested constructed objects
  addressing
* Re-work type<->codec mapping. Tags appears ambiguous. Some unique
  internal ID is needed therefore.
* Implement ANY type as an OctetString-based substrate eater

ber.decoder:
* suspend codec on underrun error ?
* class-static components map (in simple type classes)
* present subtypes ?
* component presence check wont work at innertypeconst
* optimize en/decoders
* add the rest of ASN1 types/codecs
* type vs value, defaultValue

ber.encoder:
* Asn1Item.clone() / shallowcopy issue
* large length encoder?
* codec restart
* preserve compatible API whenever stateful codec gets implemented
* restartable vs incremental
* plan: make a stateless univeral decoder, then convert it to restartable
       then to incremental

type.useful:
* may need to implement prettyIn/Out

type.char:
* may need to implement constraints

type.univ:
* simpler API to constructed objects: value init, recursive

type.namedtypes
* type vs tagset name convention

general:

* how untagged TagSet should be initialized?