POS Categories

    * POS categories filtered by pos_config
    * Visual adjustements for a 1024x768 resolution
Decrease POS orderline font-size to 12px
Ignore .DS_Store files
Add PoS Categories

    - New menus to create categories
    - New python objects for PoS Types (categories of PoS)
      and m2m relations between category <-> types

    Now, each PoS must be of a type, and each type points
    what categories of products are visible