Added lsfiles command to list all files belonging to specified package
Improved lsfiles command according to discussion from pull request (#659)
Corrected ignorePredefinedFiles condition in walk_prefix call
Corrected code to be compatible with PEP-0008

1. Adjusted names of functions and variables.
2. Rewrite compare operations of boolean values.
Merge pull request #659 from mutirri/feature-lsfiles

Added lsfiles command to list all files belonging to specified package