wndb2lmf.py script does not handle pre-3.0 versions

[goodmami]

For context: https://github.com/goodmami/wn/issues/199

There are two main issues:

• The CILI mapping format in https://github.com/globalwordnet/cili/ in older-wn-mappings/ has 3 columns instead of 2
• WordNet versions prior to 2.1 do not include verb.Framestext, so we'd need to hard-code the frames into the script

[goodmami]

A third and fourth issue for PWN 1.5:

• The Unix database files are not available, only a Windows .zip and an old Mac .bin file. For the Windows file, the filenames are all-caps and slightly different (e.g., DICT/NOUN.DAT instead of dict/data.noun), so we'd need to do some special file-loading. Luckily, there doesn't seem to be any strange encoding or line-ending problems.
• The data files don't just have the license text and data lines, but in between these two blocks there is also a list of files used to create the database. The code for reading data files needs to be made aware of this.

[goodmami]

The 3rd column of the older cili mappings is a confidence score. We should probably parse that and use it for thresholding out low-quality mappings.