allow to enumerate duplicated groups

[westram]

Sometimes taxonomic groups are splitted into multiple clades, forming duplicated groupnames. #832 suggests to use numeric suffixes separated by ~ for such groups.

ARB already supports generating such groupnames using 'group search' and an ACI using hitidx (see ​help). But this does only work for one set of duplicate groups.

Tasks:

• implement a new ACI command allowing to be applied to all duplicates in one call (e.g. report the index inside each duplicates-cluster via dupidx)
• fix predefined properties supporting numeric suffixes (still using _ instead of ~)

[westram]

by [19499]