Mark comment:entity as dynamic

Problem/Motivation

Chained comment:entity:(anything) tokens are marked as invalid even when they are not, because token validation has no context so the actual entity type is unknown.

Proposed resolution

Mark the comment:entity token as dynamic so validation skips it.

Remaining tasks

User interface changes

API changes

Data model changes

It seems to me that the comment:entity token should be marked as dynamic, because its token type depends on the entity type and tokens like comment:entity:blah are indicated as invalid although they can be resolved. When resolving, unlike when validating, the entity type is identified and successfully used to resolve the sub token.