Memleak fix

Fixes various memleaks, the decoder should run cleanly in valgrind now. Also makes it possible to reinitialize Toolbox without rereading the acoustic models.

IMPORTANT: The interface to use the decoder has a change - You have to call reinitialize_search() after reading the acoustic models and before setting any parameters. The python files in the decoder directory should show, what needs to be changed. You might also somehow bake the reading of the ph and dur files into the Toolbox constructor so that the reinitialize_search() could be automatically called there. I didn't make that change since I don't really know what you want to do.