GxPaintBox: based on GtkBox, removed unnecessary properties and functions, changed constructor signature, add missing base class destructor, use pack_start instead of add because add does not set expand any more; ParamMap: insert is private, methods have to be used to create and add parameters which are own by ParamMap (parameters are now released in the dtor); added option / Dialog to select jackd start method; reduced direct uses of global parameter_map; new class GxBuilder (replace Gtk::Builder with slightly different api); replaced some string function parameters with const string&; Parameter can allocated variable (when 0-pointer in ctor); make convolver activation more robust (when buffersize or samplerate is not yet initialized); some code moved and cleanup
