Reduce decorator/decorated function coupling in _util._disallow_empty_tables()

[ChrisKeefe]

Improvement Description
Reduce coupling by grabbing View type annotations from wrapped function signatures and using appropriate transformers instead of hard-coding acceptable view_types in the decorator.

Current Behavior
At present, _disallow_empty_tables is tightly coupled to the table view types specified by the functions it wraps. If a new view type is used for tables in a function, the decorator will need to be refactored to explicitly allow that view type.

Proposed Behavior
Introspect view type annotations in wrapped function signatures. Use get_transformer() to get a transformer to biom.Table. If none exists, fail on invalid view type/missing transformer. Else, transform to biom.Table and check is_empty() as currently.

Questions

1. Should error messages here be developer-facing (e.g. no transformer exists from View type to biom.Table) or user facing as currently implemented?

Comments
Unless we see an increase in the number of possible table View types, this 'improvement' might just be over-engineering.