Improved RTF Import

[philipt18]

I'd like to request improving RTF import capabilities. It seems APub can import index points from a Word file, but not from an RTF file. In fact you can have an RTF file with index points, import it into Word, and APub will import the index, but if you import the RTF directly, it will be ignored. It would be great to get the RTF importer at least up to date with the Word importer.

I also hope that APub will gain the ability to have multiple indexes, and then support importing multiple indexes from RTF, which supports that feature.