multiple levels of blueprint verification

[xjrc]

The design philosophy behind all of the curent conduit::blueprint::verify functions has been to approach the problem of schema validation from a data-agnostic perspective. While this makes validation straightforward and efficient, it excludes a number of more thorough checks that could be performed to more confidently report the validity of a given Blueprint hierarchy (e.g. entries in the topology and adjsets section could have their index values bounds-checked against the length of the associated coordset), which will become more relevant as the data becomes more complex (see #511, #513). These checks could be included conditionally based on user preferences, which would require adding a parameter to the conduit::blueprint::verify function to indicate a "level" of thoroughness.