- added new "operator[] const" method, useful when accessing const instances
- removed the default value (if you access an entry without first checking that
it is actually there, it's your own fault)
- replaced 'index' with 'key' which seems more logical and avoids troubles with
certain systems that #define index in their system headers
svn-id: r21430
o Implemented special alias 'prev'
o Added new calling scheme to several widgets
o Partially converted launcher dialog to new scheme
o Converted couple widgets of chooser dialog
svn-id: r21118