new arg for info: `vc info policy:all`

lists all policies that are mentioned in the config file
external scripts will need a VCtoolsDir directive, so create it
moving config from ~/.vctools.conf to ~/.vctools/vctools.conf

this allows me to add many other files in that directory
some ideas for files to put there:
-	a "last-updated" file for self-updates
-	the storage for --continue feature
-	a conf.d/ directory for assembly of configs without having to modify the central file
refactoring to create App::VC::Config->config_file()

this will return a filename (technically, a Path::Class::File object) representing a file in ~/.vctools
but, by having a method to centralize on, this makes changing it easier, should that become necessary
switching over from having the command descriptions be in the POD to having it be in the "ABSTRACT" comment

seems cleaner
added a command to update the VCtools working copy: vc self-upgrade

took the name from the perlbrew command, so hopefully it will be familiar to some
made env expansion a bit more conservative

only expand variables that are 2 or more characters and start with a letter
-	this prevents accidental expansion of things like `$1`