Add ability to update a Feed for NI Package Builder

[MaximeR]

When you create a solution with Ni Package Builder, you have the ability to create a Local Repository for a feed.

Everytime you build it it replace all.

For me, we missed a functionnality to update a feed. A feed is able to handle multiple version of a package, if you replace all, you lost the history.

Without this functionnality, you cannot mix sources of the package for the feed. In my case, I have a feed that contains package build with TS deployment tools and packages build with NI Package Builder. To include both packages, I have to build my own tool. If NI Pacakge builder was able to update existing feed, I can build all the packages of my solution and push it to the feed in one way.

Just hoping that i will have feedback !!!!