`qiime tools import`: show which formats are supported by a type

[jairideout]

Improvement Description
It'd be helpful for qiime tools import to show which format(s) can be imported into a semantic type. It's possible to use --show-importable-formats and --show-importable-types to see a complete list of importable formats and types, but it's not clear which format(s) are associated with a given --type.

References
forum x-ref