Major issues with file linking in pipeline tool

[KakCAT]

I don't know if they're documented (I've searched the issues and found nothing, but those could be there and I just didn't find them).

• Adding a folder as a link works wrong. Instead of adding the folder, and inside of it, the files it contains, it just adds all files and directories at the same level.
• When saving and reloading a project where the previous step has been performed, the containing folder disappears.
• When deleting those added files, instead of deleting the link, it tries to delete the file (i.e. in ......\file.png), which can permanently destroy data the user thinks is safe.
• When building linked data, the output directory should be defined by the pipeline tool folder structure, not the original place where the linked file is. In example, if the data is in d:\asset and the mgcb file is in d:\mgcb, and I create a directory (in the pipeline tool) named myXNB, and we create a linked file pointing to d:\asset\mytex.png inside myXNB, the output directory should be myXNB, however the pipeline tool tries to create it at d:\assets\myXNB.xnb
• Adding a file as a link just copies it (I'm not sure of it , it my just be a problem masked by the previous issues)

[KakCAT]

Closing as #5109 should fix all the problems.