Filter: Add operators to pick community components

Add operators that can be used to pick components from
pair (standard community) or lc (large community) types.
For example:

(10, 20).asn --> 10
(10, 20).data --> 20

(10, 20, 30).asn --> 10
(10, 20, 30).data1 --> 20
(10, 20, 30).data2 --> 30

Signed-off-by: Alexander Zubkov <green@qrator.net>