add play support for windows through vlc
drop duplication in name and file update (fix #15)

Sound name and filename updates are validated before the change.
Implemented the checks in a single place and call from all methods:
  * updateNameAndFile
  * changeFile
  * renameSound

Null change optimizations could be dropped to simplify code.
validate handler before renameSound (+todo)
soundcontainer.py refactoring: s#file#filename#

Rename internal parameters from file to filename.
This avoids possible conflicts with type 'file'.