Begin rewriting Entity-related code

+ Add EntityProperty
+ Add EntityUnknownProperty
+ Remove EntityField
+ Strip down EntityBox
Make entity entry viewers undockable

+ Add UndockableControl
+ Use UndockableControl in EntityEntryController
+ Periodically call Invalidate in EntityEntryViewer
Draw red points for path vertices in EntityEntryViewer
Continue rewriting Entity code

+ Add EntityPropertyLoader
+ Add EntityPropertyTypeAttribute
+ Add EntityBasicProperty
+ Add EntityBasicPropertyLoader
+ Add EntityUInt8Property
+ Add EntityUInt8PropertyLoader
+ Add EntityInt32Property
+ Add EntityInt32PropertyLoader
+ Add EntityPositionProperty
+ Add EntityPositionPropertyLoader
+ Reference System.dll in Crash
Expose the data field in EntityUnknownProperty
Add a check for Subtype presence in EntityEntryViewer
Strip the null terminator from Entity string properties
Pull the entity ID property into an Entity field

+ Add EntityID
Support a general settings (A4) field in Entity

+ Add EntitySetting
+ Add EntitySettingProperty
+ Add EntitySettingPropertyLoader
+ Add ToInt24 to BitConv
+ Add FromInt24 to BitConv
Reimplement EntityBox