Package structure

[emil14]

Enforced by compiler:

• Every entity must be either pub or used (directly or indirectly) by pub entity/main component. Entity could be both pub and "used" but cannot be unused and private at the same time.

Should be enforced by linter:

• Every neva file must be <=300 lines. Otherwise must be divided into several files. Thus small package can be single-filed but big packages must be multi-filed.
• Entities that defined in one (not shared) file must not be referenced from another (including shared) files. One file - one scope
• Entities that must be accessed from several files must be located in shared.neva file
• Shared file that is bigger that 300 lines must be, just like any other neva file, must be split into several *.shared.neva files (or separated shared sub pkg?)