xib2nib -- lot of fixes available for merge from forked repo (but can't PR)

[dkimitsa]

Hi,
I've used this tool for RoboVM linux/windows project and had fixed lot of things in it.
Sadly all this was happening in MacOS/Linux with corresponding tools used so I can't Pull Request changes as there is a risk that these will not be compatible with MS dev tools.

Commits can be cherry picked from this repo https://github.com/dkimitsa/WinObjC/tree/xib2nib by anyone interested and who has MS Dev Tools at hand.

Also I developed several tools that simplify work with nib files that makes bug fixing simpler.
Here is a technical post with tutorial https://dkimitsa.github.io/2018/02/13/wl-tech-details-2-robovm/

[DHowett-MSFT]

@dkimitsa Thanks! I'm really glad somebody's working on xib2nib!

While I'd like to just cherry-pick your changes out, we need to have potential contributors sign a contributor license agreement. If you submit a pull request -- it doesn't have to be in a mergeable format! -- we can work together on getting the right changes upstreamed.

[DHowett-MSFT]

Again, I'd like to stress not to worry if the changes can't be upstreamed. We'll do what we must to get the changes in a consumeable format, but it has to start with a pull request.

[dkimitsa]

closing as #2852 was created as mentioned by @DHowett-MSFT