Range and compound insertions/insertion-deletions

The name checker supports ranges in insertions and insertion-
deletions, for example `3_4ins8_12`, and compound insertions and
insertion-deletions, for example `3_4ins[ATC;8_12]`.
The inserted sequences are accepted and concatenated before any
further processing, so reported descriptions show only the
concatenated sequences.
The support for ranges is limited to genomic descriptions.

The position converter supports compound insertions and
insertion-deletions, not ranges.

Compound insertions and insertion-deletions are not part of the
current HGVS nomenclature, but will be proposed.