Toob Flanger, Stereo Reverb, bug fixes

- support state in factory presets.
- Use uncompressed json for settings files.
- Set current plugin preset name to last loaded plugin preset.
- Append plugins after  start node,  before end node fixed.
- Correctly release web socket when web app goes idle.
- Fit and finish issues.

src/util.hpp

@@ -29,4 +29,7 @@ namespace pipedal {
         return str.size() >= suffix.size() && 0 == str.compare(str.size()-suffix.size(), suffix.size(), suffix);
     }
     void SetThreadName(const std::string &name);
+
+    std::u32string ToUtf32(const std::string &s);
+
 }