Working annotator.py, for fast hand annotation

Use annotator.py on a pickled DataFrame of sentences, to generate JSON output recording manual annotations of categories.
Made a simpler version of annotator, with user-specified hotkeys for each choice.
Fixed line-break issues in annotator.
Removed pandas requirement from simple annotator; just reads in lines from a text file.
Added a (really) simple pre-filter script

For now, just removes tiny fragments, single words, and anything containing the word "porn".
Added option to skip existing labels when resuming