Todo:

o Page optimation of the output

  - reduce the parskip if the last page is filled less than 25%
    of the textheight
  - increase the parskip if the last page is filled more than 25%
    and less than 50% of the textheight to have it at least filled
    more than half of the textheight

o support for address database

  - adrentry and addrentry macros from KOMA-Script
  - xml files with ConTeXts contact structure

o styles

  - english and american letters in block style
  - formats from other countries

o documentation

  - description about the elements
  - examples from simple and complex letters
  - list with all named elements
  - list with the contents for the labels
  - guide how to write style and extension files
