portageq: emulate subset of Pkgcore's pquery

portageq: emulate subset of Pkgcore's pquery

Pkgcore pquery compatible options:

Repository matching options:
  --repo=REPO           repo to use (default is PORTDIR if omitted)
  --all-repos           search all repos

Package matching options:
  --herd=HERD           exact match on a herd
  --maintainer-email=MAINTAINER_EMAIL
                        comma-separated list of maintainer email regexes to
                        search for

Output formatting:
  -n, --no-version      collapse multiple matching versions together