Allow only positive allocation to or from budget - Update field validation

Purpose: It does not make sense to show a negative allocation from a budget as an increase in allocation. A negative increase should always be considered a decrease and A negative decrease should be considered an increase. Currently the only way to remove allocated value from a budget without moving it to another fund is to create a negative increase.

User story statement(s):

As a finance librarian,
I want to be able to add or remove allocation from the budget and have it display as increase or decrease
so that I know how much the budget was adjusted up or down.

Scenarios:

1. Scenario:
   • Given user has created a budget
   • When creating allocation with allocation modal
   • Then "Allocation to" is NOT always required BUT user must populate at least 1 of "Allocation to" or "Allocation from" with the budget they are currently viewing
2. Scenario:
   • Given user has created a budget
   • When creating allocation with allocation modal
   • Then amount can not be a negative number
   • AND system displays message when user adds negative
   • Message: Amount cannot be a negative value
     

Note: Currently it would show an increase in allocation of 0 and a decrease in allocation of 0. This is misleading