Store a list of built-in system addons for all releases

[rehandalal]

We need to get a list of built-in system addons with their versions for all releases of Firefox.

We will need to:

• [ ] Update the AddonGroup model with a M2M field for built-in addons.
• [ ] Get the build package zip from taskcluster
• [ ] Run a script to get the list of built-in system addons
• [ ] Create (if it does not already exist) Addon for each built-in system addon and link to the AddonGroup
• [ ] Update the AddonGroupSerializer to return the list of built-in system addons.

[rehandalal]

mshal came up with this script to parse the build package zip file:

    #! /bin/bash

    if [ $# -lt 1 ]; then
            echo "Usage: $0 package.tar.bz2" 1>&2
            exit 1
    fi

    xpis=`tar -tf $1 | grep '\.xpi'`
    tar -xf $1 $xpis
    for i in $xpis; do
            echo -n "$i: "
            unzip -c $i install.rdf 2>/dev/null | grep em:version | sed 's/<[^>]*>//g'
    done 

Usage:

$ wget https://queue.taskcluster.net/v1/task/AsU2E9KWRce1KL8WL_trvw/artifacts/public%2Fbuild%2Ffirefox-52.0a1.en-US.linux-x86_64.tar.bz2
$ ./check.sh public%2Fbuild%2Ffirefox-52.0a1.en-US.linux-x86_64.tar.bz2
./firefox/browser/features/e10srollout@mozilla.org.xpi:     1.3
./firefox/browser/features/webcompat@mozilla.org.xpi:     1.0
./firefox/browser/features/firefox@getpocket.com.xpi:     1.0.5
./firefox/browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}.xpi:     50.0