FindFiles() - replace s:find_cmd with local var of same value
Fix bug in SetNifflerMappings() in printf() call
Move OpenSelection() closer to the mappings that call it
Add directory args to Niffler() and lcd to dir for the find cmd
Refactor file_list redrawing into RedrawCandidateList() function
Move RedrawPrompt() function
Add RedrawScreen() and b:niffler_prompt to filter the list when typing
Remove TextChanged autocmd
Add Niffler command