Catalog generation and manipulation

A suite of functions that aid in constructing random catalogs, or
randomly modifying an existing catalog (wire format or parsed).

{:type       "..."
 :title      "..."
 :...        "..."
 :tags       #{"tag1", "tag2", ...}
 :parameters {:name1 "value1"
              :name2 "value2"
              ...}}

{:source       <resource spec>
 :target       <resource spec>
 :relationship <relationship id>}

{:certname    "..."
 :version     "..."
 :resources   {<resource-spec> <resource>
               <resource-spec> <resource>
               ...}
 :edges       #(<dependency-spec>,
                <dependency-spec>,
                ...)}

Puppet catalog parsing

Functions that handle conversion of catalogs from wire format to
internal PuppetDB format.

The wire format is described in detail in [the spec](../spec/catalog-wire-format.md).

There are a number of transformations we apply to wire format
catalogs during conversion to our internal format; while wire
format catalogs contain complete records of all resources and
edges, and most things are properly encoded as lists or maps, there
are still a number of places where structure is absent or lacking:

1. Resource specifiers are represented as opaque strings, like
   `Class[Foobar]`, as opposed to something like
   `{"type" "Class" "title" "Foobar"}`

2. Tags are represented as lists (and may contain duplicates)
   instead of sets

3. Resources are represented as a list instead of a map, making
   operations that need to correlate against specific resources
   unneccesarily difficult

4. Keys to all maps are strings (to conform with JSON), instead of
   more convenient Clojure keywords

### Terminology

Unless otherwise indicated, all terminology for catalog components
matches terms listed in [the spec](../spec/catalog-wire-format.md).

### Transformed constructs

### Resource Specifier (resource-spec)

A map of the form `{:type "Class" :title "Foobar"}`. This is a
unique identifier for a resource within a catalog.

### Resource

A map that represents a single resource in a catalog:

    {:type       "..."
     :title      "..."
     :...        "..."
     :tags       #{"tag1", "tag2", ...}
     :parameters {:name1 "value1"
                  :name2 "value2"
                  ...}}

Certain attributes are treated special:

* `:type` and `:title` are used to produce a `resource-spec` for
  this resource

### Edge

A representation of an "edge" (dependency or containment) in the
catalog. All edges have the following form:

    {:source       <resource spec>
     :target       <resource spec>
     :relationship <relationship id>}

A relationship identifier can be one of:

* `:contains`
* `:required-by`
* `:notifies`
* `:before`
* `:subscription-of`

### Catalog

A wire-format-neutral representation of a Puppet catalog. It is a
map with the following structure:

    {:certname    "..."
     :version     "..."
     :resources   {<resource-spec> <resource>
                   <resource-spec> <resource>
                   ...}
     :edges       #(<dependency-spec>,
                    <dependency-spec>,
                    ...)}