Chapter 3: remove restriction for input type of bound functions

Prose spec chapter 3, second-to-last paragraph new: Service-defined bound functions that take a collection as their binding parameter MAY be used as set transformations within $apply if the type of the binding parameter matches the type of the result set of the preceding transformation. If it returns a collection, further transformations can follow the bound function. The parameter syntax for bound function segments is identical to the parameter syntax for bound functions in resource path segments or $filter expressions. See section 7.6 for an example. old: Service-defined bound functions that take an entity set as their binding parameter MAY be used as set transformations within $apply if the type of the binding parameter matches the type of the result set of the preceding transformation. If it returns an entity set, further transformations can follow the bound function. The parameter syntax for bound function segments is identical to the parameter syntax for bound functions in resource path segments or $filter expressions. See section 7.6 for an example. ABNF new: customFunction = namespace "." ( entityColFunction / complexColFunction / primitiveColFunction ) functionExprParameters old: customFunction = namespace "." entityColFunction functionExprParameters