tv-get-export-path tells render tiddlers where to export files
tv-get-export-image-link tells images.js where to look for images
tv-get-export-link tells tells link.js where to look for links to other
exported tiddlers
This reverts commit b2b8006b58, reversing
changes made to e7e16137b2.
@welford my apologies it turns out there are a couple of problems, I’ll
comment more on the pull request
A bunch of little changes that together enable external image support.
Try:
```
tiddlywiki editions/tw5.com --verbose --build externalimages
```
Then open `externalimages.html`, look for the images in the more/types
tab of the sidebar, open them and verify that they are set with an
external SRC attribute, not a data URI.
