Let CPAN::Uploader load the config

This lets it handle the newly-supported situation where the .pause
file is GPG-encrypted.
cpan uploader trial?
assert that there are no errors while testing the tester

[rt.cpan.org #56831]
use Class::Load, not Class::MOP, for load_class
provide a better error when @Filter fails to load a bundle

[rt.cpan.org #56831]
if a plugin sets dynamic_config to 1, it stays on

Any kind of dynamic configuration should make the whole dist
dynamically configured.  We don't want it turned off because some
other plugin claims not to be.  Maybe this is a mistake, and we
will later revert this so that a plugin can return 0 to override
a previous decision, but it seems highly unlikely.
require bugfixed Archive::Tar::Wrapper
allow "already assign to VERSION" to be fatal
install with cpanm by default (for now)
PkgVersion: Don't attempt to save if file unchanged

PkgVersion always attempted to save the file, regardless whether
it had changed. Now, we track whether the file was successfully
munged, and only save if so. This is an optimization for the
case where no changes are made.
document die_on_existing_version
v4.300036

          read CPAN::Uploader config with CPAN::Uploader, to work with new
          trial releases supporting encrypted credential (thanks, Mike Doherty)

          improve tester tests (thanks, Dave O'Neill!)

          use Class::Load instead of Class::MOP

          better error messages when a bundle can't be loaded by @Filter

          make dynamic_config distmeta sticky; once one plugin sets it, it
          stays stuck

          add a die_on_existing_version option to PkgVersion

          switch (for now?) "dzil install" to use cpanm

          PkgVersion won't rewrite file contents if nothing was changed
          (thanks, Mike Doherty!)
stop setting repo by hand; bundle does it
v4.300037

          update repo and bugtacker URLs
drop brackets around full package name