Exclude images from the Proofing Copy RTF, they appear as large
unreadable blobs of base64 text.
Merge pull request #152 from greyelf/proofing_copy

Exclude embedded images from the Proofing Copy RTF
Fixes #57 - a least on windows. Can someone else check the other supported operating systems?
twee: Add 'stacktrace' argument to displayError()

This was added to the base class in commit b2e7bca1, but unfortunately
not added in Twee.
twee: Handle None output

This can happen if there are errors.
Converting cut, copy, and paste to use the findfocus method.
Merge pull request #153 from RichardLake/master

Fixes Ctrl-A, -X, -C, -V for the passage title textbox
Merge pull request #154 from mthuurne/twee-stacktrace

Twee error handling fixes