Replace String with PathBuf for paths

[darksv]

This PR changes handling of paths so that String is replaced with PathBuf. The latter is more suitable for this purpose as it is cross-platform and is not required to be valid UTF8. Also provides nice convenience methods like extension or join that correctly handles separators on various platforms.

[qarmin]

Changes looks mostly good.

Seems that it even fixes not excluding folders like .git by default

Also probably this is better fix to #44 than 3b63798

The only thing for now which is broken is saving to file, because it prints records with one empty line between them

---- Size 133.40 KiB (136606) - 112 files 
/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/dotbox.cur 

/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/cell.cur 

/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/row-resize.cur 

/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/ns-resize.cur 

/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/size_hor.cur 

/home/rafal/Pobrane/home/runner/work/czkawka/czkawka/gtk_app/share/icons/Adwaita/cursors/circle.cur 

[qarmin]

Windows excluded directories are broken
Sample project - Z.zip

Executing command .\czkawka_cli.exe dup -d "C:\Z" "c:/z" -e "c:/Z/Q"
finds duplicates from folder C:/z/q which should be

Found 88 duplicated files in 1 groups with same content which took 12.77 MiB:
Size - 150.29 KiB (153901) - 88 files
C:/z/fffffffffffffffffffffffffffffffffffffffffffffffffffff
C:/z/fffffffffffffffffffffffffffffffffffffffffffffffffffff (10. kopia)
C:/z/q/fffffffffffffffffffffffffffffffffffffffffffffffffffff (31. kopia)
C:/z/q/fffffffffffffffffffffffffffffffffffffffffffffffffffff (32. kopia)

On Linux ./czkawka_cli dup -d /home/rafal/Pulpit/Z /home/rafal/Pulpit/Z /home/rafal/Pulpit/Z -e /home/rafal/Pulpit/Z/Q
works as expected

[qarmin]

prettier_windows_path function was used only for normalizing path like c:/Av, c:\AV, C:/av to C:/av to allow easily remove duplicate path or overlap ones.
With PathBuf I don't think that this is necessary, and can be removed(of course if everything else will work fine)

[qarmin]

Pathbuf doesn't recognize that on Windows

"c:/z\\Q" is equal to :"c:/z/q"

and the only solution for me is to check every single time when using excluding directories if string path converted to lowerspace are equal

[darksv]

Right, I'll fix this when I got some time.

[qarmin]

You can try to rebase to current master, because I added recently CI job with checking simple regressions and it probably will allow you to test PR without needing using Windows or Wine(The longest job takes 6/7 minutes).

[darksv]

I have extracted some duplicated code related to exclusion into a separated methods. Please check whether it's OK.

[qarmin]

Seems that everything works now.
Thanks, especially for simplifying code!