Entries with translate='no' (locked) should be displayed in OmegaT

Currently the locked entries are not shown in (or event sent to) OmegaT. But they are often useful to see for the translator.

We could lock them in OmegaT with and/or add a "LOCKED SEGMENT" comment. On merge, the filter would use the original source instead of the text coming from OmegaT, so that would be safe.