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

test/contracts/multiple_contracts.aes

@@ -1,5 +1,7 @@
-contract ContractOne =
-  entrypoint foo() = "foo"
+contract Child =
+  entrypoint
+        add2 : int => int
+        add2(x) = x + 2
 
-contract ContractTwo =
-  entrypoint bar() = "bar"
+main contract Main =
+  entrypoint add4(x, c : Child) = c.add2(x) + 2