Remove backend-affecting types and reexport them from "@tesler-ui/schema"

[Dergash]

There are a lot of types that declared in Tesler UI while in fact those types describe both frontend entities and parts of screen/view/widget/sqlbc JSON descriptions which are stored in backend side of the application, which leads us to:

1. To generate JSON schemas we'll have to keep a separate instance of all the types in @tesler-ui/schema, which is a double work and will definetly end up out of sync with each outher
2. This types being declared in Tesler UI are encouraging developers to modify the public contract which is in fact also affects how Tesler API processes JSON descriptors for application entities.

Extracting them into separate repository will allow us to have a single source of truth about types affecting both frontend and JSON descriptors for application entities.

This PR adds @tesler-ui/schema and reexport those types from there so that client application could continue to referencing those types from Tesler UI.

[coveralls]

Pull Request Test Coverage Report for Build 517493683

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 58.494%

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Totals
Change from base Build 515641728:	-0.1%
Covered Lines:	3195
Relevant Lines:	4721

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💛 - Coveralls