Improvements to player selection of TargetAmount

[xenohedron]

Now, when getMultiAmount() is called within HumanPlayer::chooseTargetAmount it enforces the minimum of 1 per target to comply with CR 601.2d:

If the spell requires the player to divide or distribute an effect (such as damage or counters) among one or more targets, the player announces the division. Each of these targets must receive at least one of whatever is being divided.

chooseTargetAmount() now also prevents a human player from choosing more targets than the amount to be divided.

The spinners in PickMultiNumberDialog now start at the minimum. So when distributing among targets, they start out at 1 for each target.

The effects that call getMultiAmount() for adding mana in some combination of colors now explicitly set the minimum to 0 so they continue to work correctly.

Furthermore, for UX improvement, the PickMultiNumberDialog is bypassed when there is only one possible choice:

• If there is only one target, all damage/counters are distributed to it.
• If the number of targets is equal to the amount, each target receives 1 damage/counter.

Resolves #9379.