Redefine the value of an item, not if it exists (#127)

Asking only if an ItemizedValueDict entry exists won't ask the user the right questions; specifically letting them change the value of their dict. In this case, I've been setting up interviews to automatically define exists if asked for in this way, since usually I've been using move_checks_to_list to make objects already exist, yes / no. This means having exists and value re-edited doesn't ask two questions of the user.

Additionally, adds a default revisit question for the ALIncomeList object; otherwise edit buttons on review screens do nothing.

* Add default ALIncomeList.revisit question

docassemble/ALToolbox/data/questions/al_income.yml

@@ -117,6 +117,15 @@ subquestion: |
 
   ${ x.add_action() }
 ---
+generic object: ALIncomeList
+continue button field: x.revisit
+question: |
+  Edit incomes
+subquestion: |
+  ${ x.table }
+
+  ${ x.add_action() }
+---
 generic object: ALItemizedValueDict
 table: x.table
 rows: x
@@ -127,6 +136,7 @@ columns:
       '$0' if hasattr(row_item, 'exists') and not row_item.exists else currency(row_item.value)
 edit:
   - exists
+  - value
 ---
 generic object: ALExpenseList 
 table: x.table