bring back externals (slightly different approach), rename zotfeed to outbox...

bring back externals (slightly different approach), rename zotfeed to outbox for consistency wit AP naming. warning: this commit requires update of addons!
5 jobs for dev in 1 minute and 50 seconds (queued for 4 seconds)
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passed php7.3_mariadb10.2 #1447949

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passed php7.3_mariadb10.3 #1447950

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passed php7.3_mysql5.7 #1447947

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passed php7.3_mysql8 #1447948

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passed php7.3_postgres11 #1447951

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