change GUI

remove unneeded widgets and add a QListWidget for new UI
remove unneeded code
allow multiple files selection
implement add, delete and clear methods for files multiselection
update copyright dates
minor clean up changes
change GUI and remove some settings values
remove some settings values
small cleanups and fixes
remove unneeded code and fix MainWindow.ok_to_continue()
write better docstrings for some functions and do small cleanups
write better docstrings for some functions and other trivial changes
trivial changes
add create_paths_list()
write better docstrings for some functions
make start_conversion() to call the progress dialog
test wether files to be converted really exists
convert QStrings to unicode
version 1.5.0a1