remove duplicated use namespace::autoclean;
inserted version always has quotes
add "use_our_variable" option to [PkgVersion]
rename use_our_variable to use_our; warn of coming default change
Optimize Dist::Zilla::_check_dupe_files

Build the list of dupes in just one step while browsing the list of files.
sort found files for more repeatable build

Due to hash randomization feature in perl, the found files array will have
random order between build runs, making it more inconvenient when tracking
failures in the middle. This commit sorts the found files to remedy that.
s/ver/dist/ in tests that were clearly stolen from t/plugins/pkgversion.t - no functional changes
check for package statements first
also check for the existence of $Package::Name::VERSION in the code before adding another one
v5.026

        - eliminate use of Moose::Autobox
        - various small performance optimizations
        - add "use_our" option to PkgVersion