feat(compare): allow multiple compare blocks

[s0up4200]

Made it possible to set multiplecompare blocks via config.toml like this:

[[compare]]
host     = "100.100.100.100"
port     = 6776
login    = "user"
password = "password"

[ludviglundgren]

Some further improvements:

We could change the flag for the tag duplicates, and by doing so add the option to set a custom tag.

-command.Flags().BoolVar(&tagDuplicates, "tag", false, "tag duplicates on compare")
+command.Flags().BoolVar(&tagDuplicates, "tag-duplicates", false, "tag duplicates on compare")
+command.Flags().StringVar(&overrideTag, "tag", "", "set a custom tag for duplicates on compare")