add parse_flags function
add print_help function
Merge origin into local

Conflicts:
	renamer.lua
tentative and partial parsing of cli arguments
enlarge cli_parse with a skeleton of all functions, write check_length function
finish ispath function
return a table with command-line given files/paths
implement multi-character cli options along single-character's
write filelist function; lfs is a new dependency
write sub_spaces function
write append_str function
write prefix_str function (with the required dirname and basename)
write remove_str function
write minimize_ext function (and its dependency get_extension())
write translate_chars function
write idx_numbering function
write prepend_date function; initial working version of dateize (only predefined strings)
get_extension returns nil instead of the whole filename when file lacks an extension
fix translate_chars() different strings lenght bug
accept dates as '2012-10-01' for dateize function