Add mutli-pkg support for pkg.latest (yumpkg5)

Also made some docstring tweaks to a few other files.
Updates to yumpkg{,5}.py for multi-pkg support

Updated pkg.available_version and pkg.version to accept an arbitrary
number of arguments. pkg.available_version returns an empty string if
there is no upgrade available for that package, allowing for future
deprecation of pkg.upgrade_available.

Also reverted a change made in 585f7cc that undid a change I had
previously made in bc77261 to speed up list_pkgs().
Merge pull request #3166 from archtaku/issue2906

Add mutli-pkg support for pkg.latest (yumpkg5)
Fix #3181

If a runner accepts a keyword argument "id" or **kwargs the peer
minion executing the runner will be seen
Fix #3179
Fix #3172

This should do it!
Move logfile verification into the new verify_files function

Fix #3156
Fix available_version for apt, pacman

Per https://github.com/saltstack/salt/pull/3166#issuecomment-11957285,
change available_version so that it returns an empty string if the
available version is not an upgrade or new install.
Merge pull request #3187 from archtaku/issue2906

Fix available_version for apt, pacman
Add verify_files import to cli frontend
Remove introspection functions
Add sysmod module to replace old introspection modules

Fix #3122
Rename sys to sysmod to prevent namespace issues
Fix overlooked issues in verify_file routine