*`StreamReader.Read` methods now return errors
The other edits in this commit are related to cleaning up lint errors
caused by the changes to StreamReader
* move music path enumerations into d2resource
* move text dictionary (.tbl) loader into d2fileformats sub-package d2tbl
* lint fix, add doc file for d2tbl
* moved data_dictionary.go into d2fileformats sub-package d2txt, added doc file
* added sub-packages d2geom for geometry-related things, and d2path for path-related things
* moved calcstring.go to d2calculation
* move bitmuncher, bitstream, stream reader/writer from d2common into sub-package d2datautils
* fix lint errors in d2datadict loaders (caused by moving stuf around in d2common)
* move size.go into d2geom
* move d2common/cache.go into sub-package d2common/d2cache
* renamed d2debugutil to d2util, moved utility functions from d2common into d2util
* Reorganize MapEngine
This is already turning into a mess...
* Map engine selects tile index to use
Still very ugly
* Fix subtile flag combination
* Prepare randomly generated base tiles
* Restore collision viewer
* Movement works again, searches for straight paths
Paths are now d2vector slices
* Fix LOS calculation
* Fix test (I think)
* Unnecessary constructor assignments removed.
* Position implemented in d2common.Path
* Position implemented in mapEntity.Step.
* Position implemented in d2common.PathTile.
* DS1 reader no longer looks up objects
* Start of enteties managing their own equipment
* stringer and string2enum CompositeType
String2enum
* Use CompositeType stringer to simplify composite
* Finally fix GetDelimitedList
And lint issues
* NPC selects random equipment
* WIP: Add support for missiles
Break AnimatedEntity into two parts to support single and composite animations. Summon misssiles on right click.
* Break animated entity down further
Move npc only logic to npc struct, reduce duplication in map entities
* Change a bunch of int32s to int
