RFE: `usePackageRepositoryOptimizations` should be a repository / source option

[helge000]

The new repo optimisations in 0.10.12 do cause some issues with repositories not supporting it. 0.10.14-beta-20190321 introduced a blanket fix by disabling the feature:

choco feature disable -n usePackageRepositoryOptimizations

It would be better to introduce this setting as a per source option, like priority.

Related to #1770

[ferventcoder]

@helge000 I'd love for it to be as well. Unfortunately due to how NuGet aggregates repositories together, it's not able to be handled per source. At least not easily. I can drop this on the backlog though and we can revisit after we've moved up to NuGet v3/4.