code cleanup
add toggleoption to BuildMenu function and use it to simplify some code
require perl 5.10, use a few smart smatches
fix playlist's position not always updated when adding songs
fix songs dragged from a filesystem tab not sorted
add Stop/Quit/Turnoff-after-this-song feature

Can be found in the queue menu
Add SetNextAction command
Used by default for Stop/Quit button right-click action
add some path parsing functions and simplify code with them
clean up console error messages when song is not found
fix code mistakenly identified as translatable string
various small fixes
smarter import of playlist files and small related changes

It now tries to find a filename encoding for which all files are found
Filesystem tab: fixes and improve its responsiveness