Add first stage of a new single-file parser

This first stage consists of the general framework for the parser as
a whole, a lexical analyzers to converts text into commands, and the
semantic anlyzer to convert commands into a complete data structure
representing the cumulative effect of running the commands.

src/client/models/parsing-2/parser_extension.coffee

@@ -0,0 +1,105 @@
+#
+# Crafting Guide - parser_extension.coffee
+#
+# Copyright © 2014-2016 by Redwood Labs
+# All rights reserved.
+#
+
+########################################################################################################################
+
+module.exports = class ParserExtension
+
+    constructor: (state)->
+        @state = state
+
+    # Public Methods ###############################################################################
+
+    accepts: (command)->
+        return @_findCommandMethod(command)?
+
+    execute: w.lift (command)->
+        if not @_state? then throw new Error '@state must be defined before executing commands'
+
+        method = @_findCommandMethod command
+        method.call this, command
+
+    # Error Checking Helpers #######################################################################
+
+    alreadyExists: (command, type, id)->
+        obj = @state.get(type, id)
+        if obj?
+            @state.addError command, "a #{type} called #{id} has already been declared"
+            return true
+
+        return false
+
+    duplicateField: (command, obj, field)->
+        if obj[field]?
+            @state.addError command, "duplicate #{field}"
+            return true
+
+        return false
+
+    missingCurrent: (command, type)->
+        obj = @state.getCurrent type
+        if not obj?
+            @state.addError command, "you must declare a #{type} before using #{command.name}"
+            return true
+
+        return false
+
+    missingArgs: (command)->
+        if not command.args or command.args.length is 0
+            @state.addError command, "#{command.name} requires at least one item"
+            return true
+
+        return false
+
+    missingArgText: (command)->
+        if command.argText.length is 0
+            @state.addError command, "#{command.name} cannot be empty"
+            return true
+
+        return false
+
+    # Parsing Helpers ##############################################################################
+
+    parseBoolean: (command, text)->
+        return null unless text?
+
+        switch text.toLowerCase()
+            when "yes" then return true
+            when "no" then return false
+
+        @state.addError command, "#{command.name} requires \"yes\" or \"no\""
+        return null
+
+    parseInt: (command, text)->
+        return null unless text?
+
+        value = Number.parseInt text
+        if isNaN value
+            @addError command, "#{command.name} requires a number"
+            return null
+
+        return value
+
+    # Property Methods #############################################################################
+
+    getState: ->
+        return @_state
+
+    setState: (state)->
+        if not state? then throw new Error 'state cannot be undefined'
+        @_state = state
+
+    Object.defineProperties @prototype,
+        state: { get:@::getState, set:@::setState }
+
+    # Private Methods ##############################################################################
+
+    _findCommandMethod: (command)->
+        methodName = "_command_#{command.name}"
+        method = this[methodName]
+        return null unless _.isFunction(method)
+        return method