pkgfile: add option to match against filename or path

[solsticedhiver]

brain0 suggested:
maybe we should just have an option that allows to match the whole path
just searchmode = pkgfile.SEARCH_PACKAGE; if options.path: searchmode = pkgfile.SEARCH_PATH

[Daenyth]

I don't really think it's needed. I feel like path search is pretty intuitive and should be the default (it was with bash pkgfile) when invoked with -r or -g.

[jrstjohn]

You can close this issue because pkgfile from [extra] has replaced this pkgfile utility. Refer to #53.