Added XML originals

Added new XML originals; decided to keep them in this format rather
than .txt. Will use script to transform the originals to .txt on the
fly. Removed Apuleius files—which had been overwritten with
preprocessed files.
Preprocess script draft

First draft of a script to preproccess (xml -> txt) Perseus files.
Filename hardcoded for testing. Works for test files test_1 through
test_6.