Migrate to Abstract Syntax Trees Generator in mutator

[bugdea1er]

Use https://github.com/unified-ast/ast-generator tool in mutator

[tdv42]

after cqfn/astranaut#52 is resolved

[tdv42]

after cqfn/astranaut#52 is resolved

Resolved for now

[bugdea1er]

Waiting for cqfn/astranaut#61

[tdv42]

Waiting for cqfn/astranaut#61

Resolved for now

[bugdea1er]

API Guide: https://github.com/cqfn/astranaut/blob/master/src/main/documents/api.md

[bugdea1er]

cqfn / astranaut cannot return custom nodes from the tree transformer, so we need to implement converter both from our tree to astranaut's nodes and vice versa.
For a first demonstration a simple converter for several nodes was implemented and a simple mutation was passed to the tree transformer.

The development goes here

For the test

def bitwiseXor():
    return (5  + 4)

and the transformer rule
Binop(#1, #2)<"+"> -> Binop(#1, #2)<"-">

we got an expected result of

def bitwiseXor():
    return (5  - 4)

[tdv42]

next steps:

1. Implement converter ASTG tree to AST
2. Migrate existing migrations to ASTG
3. Add more migrations

[tdv42]

Suggested implement syntax for specifying a specific occurrence of a node in a transformation rule: cqfn/astranaut#71

[tdv42]

Waiting for cqfn/astranaut#81

[bugdea1er]

Checker module migrated to a separate repository