Add T18Entry
Add OldMusicEntry
Fix T18EntryLoader
Add T20Entry
Add new entry loaders for Crash1BetaMAY11
Fix a potential issue with display list ids in OldSceneryEntryViewer
Throw an exception if SignalError is set to return
Add TextureChunkController

+ Remove texture chunk code from LegacyController
Add T4ItemController

+ Remove LegacyController
+ Remove EditorControlAttribute
Add T15/17/18/20 entry loaders for Crash 1 retail version
Implement NSF C1 prelude support (read only)
Check to ensure only prelude chunks are compressed