Support Transkribus

[mhucka]

It should be possible to test Transkribus in this framework.

[mhucka]

After spending some time training a Transkribus model and running it, I think now this is going to be difficult to support in Handprint. It would require changing how Handprint interacts with the user, which is probably more work than is worth right now for our purposes.

[mhucka]

Deleted milestone 1.4.