refactor: unified input files handling

All commands's CLI was refactored to use new consistent handling of
input files which allows selecting multiple input files as opposed to
single archive/srcpkg:

input files as arguments:

    apkg srcpkg -a foo.1.2.tgz foo.1.2.tgz.asc

input files listed in file(s) including stdin which allows piping:

    apkg make-archive | apkg srcpkg -aF - | apkg build -sF -

Fixes: #30
Fixes: #31
7 jobs for file-list-input in 8 minutes and 45 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Test
passed flake8 #507971

00:06:05

passed integration #507975

00:06:16

passed pylint #507972

00:07:14

passed self #507974

00:06:49

passed unit #507973

00:07:23

 
  Test Py35
passed self-py35 #507977

00:01:14

passed unit-py35 #507976

00:00:48