* 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