made decode64 create useful warning dialogs on error
decode64 trys to pad selected text before processing
removed warning dialog on cancellation of write txt
added title, changed tree select mode

added title to main window
changed selectmode of file hierarchy tree to 'browse'
  this only allows one line to be selected at a time
cleaned up some code in plugins_utils
new bindings for treeview, cleaned up code

- added bindings for keyrelease of up and down on treeview
- changed varaible 'file' to something different so as to
  not shadown builtin
- parameterized more SQL