plaintext: rearrange gethsemane example files

track the pdf files for the example.
Remove the sources (because they shouldn't be distributed anyway).
Insert Gethsemane example

... and update surrounding text
plaintext: Revision run-through
plaintext: Add file format comparison

Fixes #13
plaintext: More revision

Combine introduction and abstract, some reading links, and small touches
plaintext: Final(?) revision
Merge branch 'origin/ul/plaintext'