NER fixes, code cleaning, and type hinting

[bact]

• Fix misspelled filenames in setup.py (this was previously breaks NER)
• More type hintings
• Remove repetitive functions in spellcheckers
• General code formatting
• Move old docs to docs/archive
• tcc.tcc() will now returns List[str], make it consistents with other tokenizers
• add reverse flag to collate() to do reverse sort
• isthai() (formerly is_thaiword()) and countthai() (formerly is_thai()) can now ignore customized characters (change names to make it more consistent with Python's str functions, e.g. isalpha, isdigit)
• Update docs and tests accordingly

[coveralls]

Coverage increased (+0.2%) to 81.891% when pulling 9072664 on bact:dev into e19ec28 on PyThaiNLP:dev.