add arms / legs to "sign type" selection

[kchall]

I'd like to allow the "Sign Type" selection to apply to hands, arms, or legs, as the Location and Movement modules do.

For example, this would be useful for a sign like SPACE v. 1 (p. 749 in the CD-ASL):

I'm open to suggestions about how to implement this; here is my initial suggestion.

Separate it into three tabs, for "Hands," "Arms," and "Legs." This is because the actual options for arms and legs will be different for those for hands, so trying to make any kind of universal / neutral single tab is going to be tricky.

1. The "Hands" tab is exactly as the current set of options.

2. The "Arms" tab has pretty much the analogous set, but with "arm" instead of "hand," and no options for "Hand configuration" relation:

3. The "Legs" tab is again the same as the "Arms" tab except with "leg" instead of "arm":

I also think it's actually fine if a user can access and specify elements on all three tabs. This is pretty uncharted phonological territory, so I don't want to put in too many restrictions.

[kvesik]

Some hopefully-helpful info for getting started on this issue:

• You'll be modifying the SignType GUI in class SigntypeSpecificationPanel
• You'll be modifying the SignType data structure in class Signtype
• Use QTabWidget inside the dialog-- you can see other uses of this module in class LocationOptionsSelectionPanel (via ImageTabWidget) or class PreferenceDialog.
• Feel free to copy structure/logic from the existing SignType panel (which will become the "Hands" tab) as a reference for building the "Arms" and "Legs" tabs.

Feel free to ask questions as you go!