Merge binaries

[rr-]

file_decoder and arc_unpacker should be merged into one library. What I have in mind:

arc_unpacker file

Saves file~ in its directory if it's recognized.

arc_unpacker archive

Saves archive~ in its directory if it's recognized.

arc_unpacker file archive

Saves file~ in file's directory and archive~ in archive's directory.

arc_unpacker file archive --out DIR

Saves both file~ and archive~ in DIR.

arc_unpacker --fmt=xp3 file archive

Tries to treat file and archive as xp3, if it fails - prints error (= doesn't try to guess the format by itself).

 arc_unpacker file.xp3 archive.nsa --plugin=noop

Tries to unpack file.xp3 with noop plugin, and archive.nsa with noop plugin. XP3 is unpacked successfully, while NSA is not, because there is no such plugin as noop for NSA archives.