Implement filter command

[cassava]

Currently, all filter criteria are connected by an implicit AND. Let us support OR statements.

While traditionally, | is used to signifiy or, we would like to do this in a way that is command-line friendly. Two possibilities come into mind: Accept statements like and and or, or use a comma , to signify another group.

repoctl filter a.n, a.m

[cassava]

The problem with comma is that in many disciplines, the comma is used as an and!