improve throwing of exceptions

improve code
add more debug  checks

renamed UnityEntiySubmissionScheduler

- reworked IEntityViewsDB interface, some breaking renaming and added more functions
- added two struct friendly functions as workaround while we wait for the c# byref keyworkd: QueryEntities<T> and ExecutOnEntity<T>
- fix the SwapEntityGroup function
- various optimizations
- implement a simple and efficient way to initialize entity struct values (EntityStructInitializer)
- check (in debug only) if entitystruct has only value and primitive types, otherwise throw exception
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- introduced the concept of global ID, as a combination of groupID and entityID
- only 256 groups and 2^24 entities can be created
- all the entities are now built always in group, when the group is not specified, the "standard" groups is used
- the groupID can be retrieved from the EGID
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