Feature: Add origin query

[Zweih]

Users can now query by a package's origin with where origin=<origin>.

> qp select name,version w origin=deb                                                                                                                                                
NAME              ORIGIN
libunistring2     deb
libuuid1          deb
libxxhash0        deb
libzstd1          deb
login             deb
logsave           deb
mawk              deb
mount             deb
ncurses-base      deb
ncurses-bin       deb
passwd            deb
perl-base         deb
sed               deb
sysvinit-utils    deb
tar               deb
tzdata            deb
usr-is-merged     deb
util-linux        deb
util-linux-extra  deb
less              deb

Closes #276