Contract factories and bytecode introspection (#305)

* Support for CREATE, CLONE and BYTECODE_HASH

* Add missing files

* Pushed the clone example through the typechecker

* CLONE compiles

* Fix dependent type in CLONE

* Bytecode hash fixes

* Refactor

* Refactor 2

* move some logic away

* Fixed some error messages. Type inference of child contract still does some random shit\n(mistakes arguments with result type)

* CREATE sometimes compiles and sometimes not

* Fix some scoping/constraint issues

* works, needs cleanup

* cleanup

* Fix some tests. Remove optimization of singleton tuples

* Fix default argument for clone

* Cleanup

* CHANGELOG

* Mention void type

* Address review, fix some dialyzer errors

* Please dialyzer

* Fix failing tests

* Write negative tests

* Docs

* TOC

* missing 'the'

* missing 'the'

* missing 'the'

* missing 'the'

* mention pre-fund

* format

* pre-fund clarification

* format

* Grammar in docs

CHANGELOG.md

@@ -6,7 +6,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Added
+- Child contracts
+- `Chain.clone`
+- `Chain.create`
+- `Chain.bytecode_hash`
+- Minor support for variadic functions
+- `void` type that represents an empty type
 ### Changed
+- Contract interfaces must be now invocated by `contract interface` keywords
+- `main` keyword to indicate the main contract in case there are child contracts around
+- `List.sum` and `List.product` no longer use `List.foldl`
 ### Removed
 
 ## [5.0.0] 2021-04-30