Restrict read/write from type statements.

[mckoss]

The current version of Bolt (after 0.4) allows read() and write() expressions in type statements. Since these are not explicitly "schema" based (more authorization than schema), this could cause rules to be created that are not portable or easy to maintain.

The counter example is the chat.bolt sample.

This experiment intermixes validate(), read() and write() rules in various type expressions. The advantage being that you don't have to repeat the path structure in two places (once in path statement, and again in the type containment hierarchy).

One proposal is to introduce user-defined methods within types to allow for not repeating "behavior" in path statments - but this still does not resolve the issue with duplicating the two storage hierarchies.