Provide a way to enter justification for each proposal item within proposal group

[ribose-jeffreylau]

... instead of just one justification for the entire group.

from discussion with @maccraymer

[maccraymer]

Thinking about this more, it should be sufficient to simply use a single justification for the proposal group as the justification for all the individual items. Note that once the group of items is accepted in to the registry, each item will be a standalone entry and the concept of the group will be lost. Each of those items needs its own justification. But because the items are being submitted as a single group where items are presumably related to each other in some way, it should be possible to come up with a single general justification to use for all the items in the group. -Mike