ActionImport and FunctionImport on EntityType

We allow calling bound actions/functions with qualified name, or with unqualified (short) name if the namespace defining the function is marked as the default namespace. In the latter case we need precedence rules if action/function names collide with property names.

This can be avoided if an entity type can actively declare which actions/functions it allows by "importing" the (still global) action/function into the type, similar to what we currently do in the entity container.

This has several benefits:

• explicitly declare support for bound actions/functions
• provide clash-free short name for bound action/function
• harmonize entity container and entity type