Merging both the internal and external approach

Merging both the integrated and external verifier approach.

In this Merge Request the elm-ast-to-smt-input folder has been moved into elm-verify and been renamed to elm-verify-inetgrated and now depends on the elm-compiler-library module in elm-verify.

The submodule for the elm-compiler-lib has both versions merged and adjusted to build both an executable (for integrated approach) and a library (for external approach).

Both approaches have been adjusted to be able to compile together.

• integrated uses changed artifact type
• external uses the Verify type which has been moved to elm-data to Skip integrated verification

A dependencies map has been added in elm-verify

It would be nice if @tim ,@kaiprott and @stu114663 could review this merge request. This merge request is linked to the corresponding one in the submodule stu201758/elm-compiler-library!1