Generics in Kotlin codegen #88

Description

Extract type variables from the available structures inside the engine and put them into the result model.

Expected behavior

Kotlin code should be generated with generics where it is required.
Framework tests should pass with compilation for Kotlin enabled.
Additional testing on contest estimator is to be done.

Environment

Not applicable

Potential alternatives

Not applicable

Context

Generic types are much more often required in Kotlin than in Java(e.g. collections), so additional support for them is to be made.
Currently, generated Kotlin code does not use generics, and thus a lot of code does not compile.