Return message for searches for complex variants

[nawatts]

gnomAD contains only SNVs/indels. However, the browser search allows entering a complex variant in chrom-pos-ref-alt format or a ClinGen CAID or ClinVar variation ID for a complex variant. If such a variant is entered, display a message explaining that complex variants will not appear in gnomAD.

Searches for MNVs should still work though.