Removed createTag in favor of custom functions for each collection.

Each item collection XYZ with keys of generated functions cncCreateItem_XYZ and cncPut_XYZ, customized based on the item type and the shape of the item key. Each step collection ABC has a generated function cncPrescribe_ABC, customized based on the shape of the step tag. These changes allow the compiler to check for the correct type and shape of tags and keys, and also allows us to store tags/keys internally as integer values rather than cstrings.