Pybcpy

- PEP 8
- added (first draft) new toolkit `pyusrgrptk` for backup user group information
- `pyusrgrptk` methods for searching, or listing all groups
- hierarchy view of all groups
- list group with, or without member
- list only group member (use with filter)
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- restore of files
- save and restore of Linux access controll list information with module
[`acl-toolkit`](https://github.com/kr-g/pybcpy/tree/master/pyacltk)
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- added list detail cmd
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BACKLOG

- quite mode
- rework logging info, level, and behaviour
- catch exception for intermediate deleted files during bak process
- stats also for other tasks
- partial backup -> inner sub folder
- proper testing pending. if execution breaks please create an issue on github.
- ~~no restore supported as of now.~~
- ~~no support of permission objects e.g. ACLs, or Groups.~~
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KNOWN BUGS

- delete dir in repo fails when not empty
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LIMITATIONS

- proper error messages, read exception error text properly
- no grafical (GUI) tool available, only cmd-line.
- no restore from a tar-mode backup repo
- tar mode is added as experimental feature (might be dropped in future)
- no full support of empty directories.
- no logging to syslog.
- no file chunk difference calculation for big files.
- no SSH, FTP, HTTP support. use of mounted device only.
- no support for excluding sub-directories.
- no root directory backup support.
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