* Flesh out the formerly incomplete ItemSlug class
* Convert all uses of text item slugs to use ItemSlug
* Move the ItemSlug class under models where it properly belongs
* Avoid the use of `slug` as a local variable or item attribute
wherever possible to avoid confusion between various kinds of slugs
* Merge the InventoryParser class into the Inventory class as it is
unlikely to need to support multiple versions
* Simplify the ModPack/Mod/ModVersion interfaces by replacing the use
of various "helper" methods with equivalent use of more generic
methods
* Update the various methods of ModPack/Mod/ModVersion to be able to
work with qualified or unqualified ItemSlugs
* Remove the unused BaseCollection class
* Add tests for ItemSlug and update all other tests to reflect
all the other changes
* Remove V1 of the mod version parser and shift V2 up to be V1
* Add a parser for mod.cg files, and refactor the the mod-version.cg
files to push the appropriate content up to the mod.cg
* Remove the concept of "silent" from BaseModel along with logging
each event as they are fired (which is what really prompted the
need for it in the first place)
* Move use of the Storage class to be completely the province of the
controllers most closely related to models affected
* Convert the ModVersionController to the ModController and have it
take on responsibility for choosing the mod version
* Update BaseModel to support simple accessors for the current state
* Update CraftingPlan to be able to remove uncraftable items
* Implement the Mod model
* Tweak style of quantity label in output box to be more visible
* Move data files for all mods under a directory for the specific
version of the mod
* Add a `silent` property to the base model to prevent models which
shouldn't be observed from emitting events
* Change the term "itemSlug" to just "slug" across the board
* Change all models so that they don't require their parent in their
constructors and so that they don't automatically add themselves to
their parents lists
* Remove a bunch of unnecessary event triggering
* Tighten up access to various lists of children across all models
* Refactor the guts of the V2 parser into an abstract base class so
it can be used for other parsers in the future
* Remove a number of unused methods
* Refactor location of all data files to include a subdirectory
for the mod version
* Update the BaseModel class to allow models to load themselves from
any text file (whether JSON or CG)
* Refactor ModPack & ModVersion to move the laoding functionality in
one into the other (and use the new stuff in BaseModel)
* Move the parser versions into a new subdirectory which allows for
future additional parsers
* Revert the local storage change as it ties model objects to global
state and makes testing impossible. It will be necessary to redo
that feature differently
* Refactor the parser versions to move V1 into its own set of files