Parameter is now a generic abstract class.
Parameter now receives an initial value.
Parameter has now another parseValue abstract method taking a
String as an argument.

This is for better usability with the ParameterEditor.
Create DoubleParameter class.
parseValue(String) now uses the parseValue(Double).
setValue in Parameter now return true if the value is updated.
Sound now uses DoubleParameter to handle frequency, duration and
amplitude.
Add getParameters method to Sound.
Add getParameter method to ParameterEditor.
Add a new setValue method taking a String has argument.
Updatet player to the new Sound API with getParameterByName.
Now possible to get a Sound Parameter by name.
ParameterEditor is no longer an Observer of Sound.

All the graphical updates are done directly into the Parameter objects.
Parameter now receive its Observer as a parameter.
Adapts Sound constructor to the new Parameter API.
Sound now regenerate signal on Parameter update as well as Modifier.
Merge branch 'master' of https://github.com/remigourdon/sound-editors