* improve AssetManager implementation
Notable changes are:
* removed the individual managers inside of d2asset, only one asset manager
* AssetManager now has caches for the types of files it loads
* created a type for TextDictionary (the txt file structs)
* fixed a file path bug in d2loader Source
* fixed a asset stream bug in d2loader Asset
* d2loader.Loader now needs a d2config.Config on creation (for resolving locale files)
* updated the mpq file in d2asset test data, added test case for "sub-directory"
* added a Data method to d2asset.Asset. The data is cached on first full read.
* renamed ArchiveDataStream to DataStream in d2interface
* moved palette utility func out of d2asset and into d2util
* bugfix for MacOS mpq loader issue
* minor lint fixes
* removed obsolete interfaces from d2interface
* lint fixes, added data caching to filesystem asset
* adding comment for mpq asset close
* adding comment for mpq asset close
