Add window functions to spectrum

[aparnaaaahhh]

Implemented support for window functions by updating the navigation menu and the corresponding Java classes.

[billthefarmer]

Thank you. I will implement this using your code in the spectrum activity, but not as you have done it for several reasons:

• You have put the selection in the app navigation menu rather than in the spectrum overflow menu.
• You have put code in the scope app which is redundant.
• You have used embedded strings in code and the menu.

Edit: Having looked at the code, it should be in the preferences.