change containers to work with DB description

   instead of saving all data in widget itself
TODO up
fix database after changes in upstream
save list of classes, which are containers widget inherits from
small renaming of function
add wdg_is_container()
fixing const stuff
remove IS_BOX/IS_TABLE macro
fix to save right pointer to classes namew
change some variable's names
add Elm_Container as container to database
refactoring class descriptions to store in hash
move inherits list from widget to class description
create empty field for content depending on container
add little bit details
refactoring
fix case when GUI_TYPE_STRING value is GUI_TYPE_NULL
update database, add content_unset func
content_unset need special attitude
fix in unpacking