Load backup configuration from file

[KyrietS]

Config file should include things like:

• Backup path (absolute or relative to config file) [optional*]
• List of paths to back up.
• Flag, if logs should be captured and stored with snapshots. [separate feature]
• Compression method [separate feature]

* I should consider ability to place config file into a backup folder. In this situation backup path won't be necessary. What's more this config could be read automatically when running mizeria /path/to/backup --run or something.

[KyrietS]

Suggestion to use toml as a config file format.