Add multiple shortening path methods
Add multiple shortening path methods

"truncate_chars_from_path_left" is supposed to be the Liquidprompt v1
default. "dirs_from_path_right" is supposed to work like setting
LP_PATH_KEEP=-1 (not implemented yet).

pkkolos/liquidprompt,nojhan/liquidprompt,jaesivsm/liquidprompt,milouse/liquidprompt,laurentbardin/liquidprompt