Show variables in sorted order, and widen the forms

Sometimes I cannot find a variable when I'm editing a node or group, and when I do find it, the field is too narrow to see the whole variable name. This sorts the variables in the edit screen (they are already sorted in the view screen!) and widens the forms to the page width.

Before:
![Screen Shot 2013-04-27 at 2 12 05 PM](https://f.cloud.github.com/assets/39406/434913/38adbbf0-af7f-11e2-8e29-651356cc4b90.png)

After:
![Screen Shot 2013-04-27 at 2 11 49 PM](https://f.cloud.github.com/assets/39406/434912/389c5568-af7f-11e2-89fc-38c4f8edd9b6.png)