Fix bug with link node references

Looks like I was working with an old data source that saved the whole
`source` and `target` nodes inside the link instead of just the index
values. Fixed.
Change format of relationship descriptors

Basically just made sure they were all going the right direction. More
relevant to the data than the application.
IMPORTANT!!! Gitignore deleting stuff weirdness

So I inadvertently stashed stuff (switched branches with an uncommitted
change in the GUI) which apparently runs `gitclean -d`, which removes
untracked files/folders. I had not ignored the data folder but had
ignored the extensions of all of the files in it (*.json and *.csv). My
data folder was gone! And since the files weren't tracked I couldn't
roll back to it. Fortunately there was nothing irreplacable in there
but there could have been. <a
href="http://blog.icefusion.co.uk/git-stash-can-delete-ignored-files-git
-stash-u/">This post</a> says that /directory/* gets you in trouble
while /directory is safe. My "versions" directory stayed put, which was
ignored like this: `versions/'. I'm changing it to the other format
just to be safe.